Purpose: The ⁶⁸Ga-PSMA PET/CT is a commonly used imaging modality in prostate cancers. However, few studies have compared the diagnostic efficiency between ⁶⁸Ga-PSMA and ¹⁸F-FDG PET/CT and evaluated whether a heterogeneous metabolic phenotype (especially PSMA-FDG+ lesions) exists in patients with castration-resistant prostate cancer (CRPC). We determined the added value of ¹⁸F-FDG PET/CT compared to ⁶⁸Ga-PSMA PET/CT in CRPC patients and identified CRPC patients who may benefit from additional ¹⁸F-FDG PET/CT. Methods: Data of 56 patients with CRPC who underwent both ⁶⁸Ga-PSMA and ¹⁸F-FDG PET/CT from May 2018 to February 2021 were retrospectively analysed. Patients were classified into two groups with or without PSMA-FDG+ lesions. The differences in patient characteristics between the two groups and predictors of patients who having at least one PSMA-FDG+ lesion were analysed. Results: Although both the detection rate (75.0% vs. 51.8%, P = 0.004) and positive lesion number (135 vs. 95) of ⁶⁸Ga-PSMA PET/CT were higher than ¹⁸F-FDG PET/CT, there were still 13/56 (23.2%) patients with at least one PSMA-FDG+ lesion. The prostate-specific antigen (PSA) and Gleason score were both higher in the patients with PSMA-FDG+ lesions than in those without PSMA-FDG+ lesions (P = 0.04 and P<0.001, respectively). Multivariate regression analysis showed that the Gleason score (≥8) and PSA (≥7.9 ng/mL) were associated with the detection rate of patients who had PSMA-FDG+ lesions (P = 0.01 and P = 0.04, respectively). The incidences of having PSMA-FDG+ lesions in low-probability (Gleason score<8 and PSA<7.9 ng/mL), medium-probability (Gleason score≥8 and PSA<7.9 ng/mL or Gleason score<8 and PSA≥7.9 ng/mL), and high-probability (Gleason score≥8 and PSA≥7.9 ng/mL) groups were 0%, 21.7%, and 61.5%, respectively (P<0.001). Conclusion: Gleason score and PSA are significant predictors for PSMA-FDG+ lesions, and CRPC patients with high Gleason score and PSA may benefit from additional ¹⁸F-FDG PET/CT.

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PREAMBLE

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional nonprofit medical association that facilitates communication worldwide between individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. The EANM was founded in 1985. SNMMI and EANM members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine.

The SNMMI and EANM will periodically define new guidelines for nuclear medicine practice to help advance the science of nuclear medicine and to improve the quality of service to patients throughout the world. Existing practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated.

Each practice guideline, representing a policy statement by the SNMMI/EANM, has undergone a thorough consensus process in which it has been subjected to extensive review. The SNMMI and EANM recognize that the safe and effective use of diagnostic nuclear medicine imaging requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guideline by those entities not providing these services is not authorized.

These guidelines are an educational tool designed to assist practitioners in providing appropriate care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, both the SNMMI and the EANM caution against the use of these guidelines in litigation in which the clinical decisions of a practitioner are called into question.

The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by the physician or medical physicist in light of all the circumstances presented. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the guidelines.

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Therefore, it should be recognized that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.

Visual Abstract

Visual Abstract

Methods to shorten [¹⁸F]FDG Patlak PET imaging procedures ranging from 65–90 to 20–30 min after injection, using a population-averaged input function (PIF) scaled to patient-specific image-derived input function (IDIF) values, were recently evaluated. The aim of the present study was to explore the feasibility of ultrashort 10-min [¹⁸F]FDG Patlak imaging at 55–65 min after injection using a PIF combined with direct Patlak reconstructions to provide reliable quantitative accuracy of lung tumor uptake, compared with a full-duration 65-min acquisition using an IDIF. Methods: Patients underwent a 65-min dynamic PET acquisition on a long-axial-field-of-view (LAFOV) Biograph Vision Quadra PET/CT scanner. Subsequently, direct Patlak reconstructions and image-based (with reconstructed dynamic images) Patlak analyses were performed using both the IDIF (time to relative kinetic equilibrium between blood and tissue concentration (t*) = 30 min) and a scaled PIF at 30–60 min after injection. Next, direct Patlak reconstructions were performed on the system console using only the last 10 min of the acquisition, that is, from 55 to 65 min after injection, and a scaled PIF using maximum crystal ring difference settings of both 85 and 322. Tumor lesion and healthy-tissue uptake was quantified and compared between the differently obtained parametric images to assess quantitative accuracy. Results: Good agreement was obtained between direct- and image-based Patlak analyses using the IDIF (t* = 30 min) and scaled PIF at 30–60 min after injection, performed using the different approaches, with no more than 8.8% deviation in tumor influx rate value (K_i) (mean difference ranging from –0.0022 to 0.0018 mL/[min x g]). When direct Patlak reconstruction was performed on the system console, excellent agreement was found between the use of a scaled PIF at 30–60 min after injection versus 55–65 min after injection, with 2.4% deviation in tumor K_i (median difference, –0.0018 mL/[min x g]; range, –0.0047 to 0.0036 mL/[min x g]). For different maximum crystal ring difference settings using the scan time interval of 55–65 min after injection, only a 0.5% difference (median difference, 0.0000 mL/[min x g]; range, –0.0004 to 0.0013 mL/[min x g]) in tumor K_i was found. Conclusion: Ultrashort whole-body [¹⁸F]FDG Patlak imaging is feasible on an LAFOV Biograph Vision Quadra PET/CT system without loss of quantitative accuracy to assess lung tumor uptake compared with a full-duration 65-min acquisition. The ultrashort 10-min direct Patlak reconstruction with PIF allows for its implementation in clinical practice.

Quantification of ¹⁸F-FDG PET images is useful for accurate diagnosis and evaluation of various brain diseases, including brain tumors, epilepsy, dementia, and Parkinson disease. However, accurate quantification of ¹⁸F-FDG PET images requires matched 3-dimensional T₁ MRI scans of the same individuals to provide detailed information on brain anatomy. In this paper, we propose a transfer learning approach to adapt a pretrained deep neural network model from amyloid PET to spatially normalize ¹⁸F-FDG PET images without the need for 3-dimensional MRI. Methods: The proposed method is based on a deep learning model for automatic spatial normalization of ¹⁸F-FDG brain PET images, which was developed by fine-tuning a pretrained model for amyloid PET using only 103 ¹⁸F-FDG PET and MR images. After training, the algorithm was tested on 65 internal and 78 external test sets. All T₁ MR images with a 1-mm isotropic voxel size were processed with FreeSurfer software to provide cortical segmentation maps used to extract a ground-truth regional SUV ratio using cerebellar gray matter as a reference region. These values were compared with those from spatial normalization-based quantification methods using the proposed method and statistical parametric mapping software. Results: The proposed method showed superior spatial normalization compared with statistical parametric mapping, as evidenced by increased normalized mutual information and better size and shape matching in PET images. Quantitative evaluation revealed a consistently higher SUV ratio correlation and intraclass correlation coefficients for the proposed method across various brain regions in both internal and external datasets. The remarkably good correlation and intraclass correlation coefficient values of the proposed method for the external dataset are noteworthy, considering the dataset’s different ethnic distribution and the use of different PET scanners and image reconstruction algorithms. Conclusion: This study successfully applied transfer learning to a deep neural network for ¹⁸F-FDG PET spatial normalization, demonstrating its resource efficiency and improved performance. This highlights the efficacy of transfer learning, which requires a smaller number of datasets than does the original network training, thus increasing the potential for broader use of deep learning–based brain PET spatial normalization techniques for various clinical and research radiotracers.

Our purpose was to prospectively assess the distribution of NETPET scores in well-differentiated (WD) grade 2 and 3 gastroenteropancreatic (GEP) neuroendocrine tumors (NETs) and to determine the impact of the NETPET score on clinical management. Methods: This single-arm, institutional ethics review board–approved prospective study included 40 patients with histologically proven WD GEP NETs. ⁶⁸Ga-DOTATATE PET and ¹⁸F-FDG PET were performed within 21 d of each other. NETPET scores were evaluated qualitatively by 2 reviewers, with up to 10 marker lesions selected for each patient. The quantitative parameters that were evaluated included marker lesion SUV_max for each tracer; ¹⁸F-FDG/⁶⁸Ga-DOTATATE SUV_max ratios; functional tumor volume (FTV) and metabolic tumor volume (MTV) on ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET, respectively; and FTV/MTV ratios. The treatment plan before and after ¹⁸F-FDG PET was recorded. Results: There were 22 men and 18 women (mean age, 60.8 y) with grade 2 (n = 24) or grade 3 (n = 16) tumors and a mean Ki-67 index of 16.1%. NETPET scores of P0, P1, P2A, P2B, P3B, P4B, and P5 were documented in 2 (5%), 5 (12.5%), 5 (12.5%) 20 (50%), 2 (5%), 4 (10%), and 2 (5%) patients, respectively. No association was found between the SUV_max of target lesions on ⁶⁸Ga-DOTATATE and the SUV_max of target lesions on ¹⁸F-FDG PET (P = 0.505). ¹⁸F-FDG/⁶⁸Ga-DOTATATE SUV_max ratios were significantly lower for patients with low (P1–P2) primary NETPET scores than for those with high (P3–P5) primary NETPET scores (mean ± SD, 0.20 ± 0.13 and 1.68 ± 1.44, respectively; P < 0.001). MTV on ¹⁸F-FDG PET was significantly lower for low primary NETPET scores than for high ones (mean ± SD, 464 ± 601 cm³ and 66 ± 114 cm³, respectively; P = 0.005). A change in the type of management was observed in 42.5% of patients after ¹⁸F-FDG PET, with the most common being a change from systemic therapy to peptide receptor radionuclide therapy and from debulking surgery to systemic therapy. Conclusion: There was a heterogeneous distribution of NETPET scores in patients with WD grade 2 and 3 GEP NETs, with more than 1 in 5 patients having a high NETPET score and a frequent change in management after ¹⁸F-FDG PET. Quantitative parameters including ¹⁸F-FDG/⁶⁸Ga-DOTATATE SUV_max ratios in target lesions and FTV/MTV ratios can discriminate between patients with high and low NETPET scores.

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic tumors for which standardized diagnostic work-up fails to identify the primary site. We aimed to describe the Peter MacCallum Cancer Centre experience with ¹⁸F-FDG PET/CT in extracervical CUP with respect to detection of a primary site and its impact on management. A secondary aim was to compare overall survival (OS) in patients with and without a detected primary site. Methods: CUP patients treated between 2014 and 2020 were identified from medical oncology clinics and ¹⁸F-FDG PET/CT records. Information collated from electronic medical records included the suspected primary site and treatment details before and after ¹⁸F-FDG PET/CT. Clinicopathologic details and genomic analysis were used to determine the clinically suspected primary site and compared against 2 independent masked reads of ¹⁸F-FDG PET/CT images by nuclear medicine specialists to determine sensitivity, specificity, accuracy, and the rate of detection of the primary site. Results: We identified 147 patients, 65% of whom had undergone molecular profiling. The median age at diagnosis was 61 y (range, 20–84 y), and the median follow-up time was 74 mo (range, 26–83 mo). Eighty-two percent were classified as having an unfavorable CUP subtype as per international guidelines.¹⁸F-FDG PET/CT demonstrated a primary site detection rate of 41%, resulted in a change in management in 22%, and identified previously occult disease sites in 37%. Median OS was 16.8 mo for all patients and 104.7 and 12.1 mo for favorable and unfavorable CUP subtypes, respectively (P < 0.0001). Median OS in CUP patients when using ¹⁸F-FDG PET/CT, clinicopathologic, and genomic information was 19.8 and 8.5 mo when a primary site was detected and not detected, respectively (P = 0.016). Multivariable analysis of survival adjusted for age and sex remained significant for identification of a potential primary site (P < 0.001), a favorable CUP (P < 0.001), and an Eastern Cooperative Oncology Group status of 1 or less (P < 0.001). Conclusion: ¹⁸F-FDG PET/CT plays a complementary role in CUP diagnostic work-up and was able to determine the likely primary site in 41% of cases. OS is improved with primary site identification, demonstrating the value of access to diagnostic ¹⁸F-FDG PET/CT for CUP patients.

Neoadjuvant therapy in patients with locally advanced rectal cancer (LARC) has achieved good pathologic complete response (pCR) rates, potentially eliminating the need for surgical intervention. This study investigated preoperative methods for predicting pCR after neoadjuvant short-course radiotherapy (SCRT) combined with immunochemotherapy. Methods: Treatment-naïve patients with histologically confirmed LARC were enrolled from February 2023 to July 2023. Before surgery, the patients received neoadjuvant SCRT followed by 2 cycles of capecitabine and oxaliplatin plus camrelizumab. ⁶⁸Ga-labeled fibroblast activation protein inhibitor ([⁶⁸Ga]Ga-FAPI-04) PET/MRI, [¹⁸F]FDG PET/CT, and contrast-enhanced MRI were performed before treatment initiation and before surgery in each patient. PET and MRI features and the size and number of lesions were also collected from each scan. Each parameter’s sensitivity, specificity, and diagnostic cutoff were derived via receiver-operating-characteristic curve analysis. Results: Twenty eligible patients (13 men, 7 women; mean age, 60.2 y) were enrolled and completed the entire trial, and all patients had proficient mismatch repair or microsatellite-stable LARC. A postoperative pCR was achieved in 9 patients (45.0%). In the visual evaluation, both [⁶⁸Ga]Ga-FAPI-04 PET/MRI and [¹⁸F]FDG PET/CT were limited to forecasting pCR. Contrast-enhanced MRI had a low sensitivity of 55.56% to predict pCR. In the quantitative evaluation, [⁶⁸Ga]Ga-FAPI-04 change in SUL_peak percentage, where SUL_peak is SUV_peak standardized by lean body mass, had the largest area under the curve (0.929) with high specificity (sensitivity, 77.78%; specificity, 100.0%; cutoff, 63.92%). Conclusion: [⁶⁸Ga]Ga-FAPI-04 PET/MRI is a promising imaging modality for predicting pCR after SCRT combined with immunochemotherapy. The SUL_peak decrease exceeding 63.92% may provide valuable guidance in selecting patients who can forgo surgery after neoadjuvant therapy.

This study evaluates the diagnostic utility of PET/MRI for primary, locoregional, and nodal head and neck squamous cell carcinoma (HNSCC) through systematic review and metaanalysis. Methods: A systematic search was conducted using PubMed and Scopus to identify studies on the diagnostic accuracy of PET/MRI for HNSCC. The search included specific terms and excluded nonhybrid PET/MRI studies, and those with a sample size of fewer than 10 patients were excluded. Results: In total, 15 studies encompassing 638 patients were found addressing the diagnostic test accuracy for PET/MRI within the chosen subject domain. Squamous cell carcinoma of the nasopharynx was the most observed HNSCC subtype (n = 198). The metaanalysis included 12 studies, with pooled sensitivity and specificity values of 93% and 95% per patient for primary disease evaluation, 93% and 96% for locoregional evaluation, and 89% and 98% per lesion for nodal disease detection, respectively. An examination of a subset of studies comparing PET/MRI against PET/CT or MRI alone for evaluating nodal and locoregional HNSCC found that PET/MRI may offer slightly higher accuracy than other modalities. However, this difference was not statistically significant. Conclusion: PET/MRI has excellent potential for identifying primary, locoregional, and nodal HNSCC.

The tumor marker cancer antigen 15-3 (CA 15-3) is that most commonly used to monitor metastatic breast cancer during active therapy and surveillance for disease recurrence after treatment. The association of CA 15-3 and ¹⁸F-FDG PET/CT findings can be considered complementary, since any significant rise may indicate the presence of disease and imaging is able to map the tumor sites. Although current guidelines do not recommend the routine performance of CA 15-3 in asymptomatic patients being followed up after definitive breast cancer treatment, most oncologists perform serial assessment of the tumor markers as part of routine follow-up of patients. The aim of this study was to evaluate the correlation between CA 15-3 levels and ¹⁸F-FDG PET/CT scan findings in patients with recurrent breast cancer. Methods: This was a cross-sectional study with data collected retrospectively. Patients being evaluated for breast cancer recurrence with ¹⁸F-FDG PET/CT imaging and CA 15-3 level were included. Evaluation of the association between CA 15-3 levels and ¹⁸F-FDG PET/CT scan findings was then done. Results: In total, 154 cases were included in this study; 62 patients had recurrence (positive) on the ¹⁸F-FDG PET/CT scans, whereas 92 patients had normal (negative) findings on follow-up ¹⁸F-FDG PET/CT scans. There was an association between CA 15-3 levels and the presence or absence of recurrence on ¹⁸F-FDG PET/CT scans, with 84.4% (27/32) of patients who had elevated CA 15-3 levels having disease recurrence on ¹⁸F-FDG PET/CT and 84.4% (27/32) of patients who had elevated CA 15-3 levels having disease recurrence on ¹⁸F-FDG PET/CT as well as a correlation with the burden of metastases. Most patients with disease recurrence on ¹⁸F-FDG PET/CT, however, had normal CA 15-3 levels. Conclusion: Higher CA 15-3 levels correlate with breast cancer recurrence on ¹⁸F-FDG PET/CT as well as with burden of metastasis. Notably, CA 15-3 levels within the reference range do not exclude breast cancer disease recurrence since more than half of patients with recurrence had normal CA 15-3 levels. ¹⁸F-FDG PET/CT should therefore be considered in patients with suspected breast cancer recurrence but normal CA 15-3 levels.

Numerous recent works highlight the limited utility of established tumor cell lines in recapitulating the heterogeneity of tumors in patients. More realistic preclinical cancer models are thought to be provided by transplantable, patient-derived tumor xenografts (PDX). Inter- and intra-tumor heterogeneity of PDX, however, present several challenges in developing optimal quantitative pipelines to assess response to therapy. The objective of this work was to develop and optimize image metrics of FDG-PET to assess response to combination docetaxel/carboplatin therapy in a co-clinical trial involving triple negative breast cancer (TNBC) PDX. We characterize the reproducibility of SUV metrics to assess response to therapy and optimize a preclinical PERCIST (µPERCIST) paradigm to complement clinical standards. Considerations in this effort included variability in tumor growth rate and tumor size; solid tumor vs. tumor heterogeneity and necrotic phenotype; and optimal selection of tumor slice versus whole tumor. A test-retest protocol was implemented to optimize the reproducibility of FDG-PET SUV thresholds, SUVpeak metrics, and µPERCIST parameters. In assessing response to therapy, FDG-PET imaging was performed at baseline and +4 days following therapy. The reproducibility, accuracy, variability, and performance of imaging metrics to assess response to therapy were determined. We defined an index—"Quantitative Response Assessment Score (QRAS)"—to integrate parameters of prediction and precision, and thus aid in selecting optimal image metrics of response to therapy. Our data suggests that a threshold value of 25% (SUV25) of SUVmax was highly reproducible (<9% variability). Concordance and reproducibility of µPERCIST were maximized at α=0.7 and β=2.8 and exhibited high correlation to SUV25 measures of tumor uptake. QRAS scores favor SUV25 followed by SUVP14 as optimal metrics of response to therapy. Additional studies are warranted to fully characterize the utility of SUV25 and µPERCIST SUVP14 as image metrics of response to therapy across a wide range of therapeutic regiments and PDX models.

Purpose: The aim of this retrospective multicentric study was to develop and evaluate a prognostic FDG PET/CT radiomics signature in early-stage non-small cell lung cancer (NSCLC) patients treated with stereotactic radiotherapy (SBRT). Material and Methods: Patients from 3 different centers (n = 27, 29 and 8) were pooled to constitute the training set, whereas the patients from a fourth center (n = 23) were used as the testing set. The primary endpoint was local control (LC). The primary tumour was semi-automatically delineated in the PET images using the Fuzzy locally adaptive Bayesian algorithm, and manually in the low-dose CT images. A total of 184 IBSI-compliant radiomic features were extracted. Seven clinical and treatment parameters were included. We used ComBat to harmonize radiomic features extracted from the four institutions relying on different PET/CT scanners. In the training set, variables found significant in the univariate analysis were fed into a multivariate regression model and models were built by combining independent prognostic factors. Results: Median follow-up was 21.1 (1.7 – 63.4) and 25.5 (7.7 – 57.8) months in training and testing sets respectively. In univariate analysis, none of the clinical variables, 2 PET and 2 CT features were significantly predictive of LC. The best predictive models in the training set were obtained by combining one feature from PET, namely information correlation 2 (IC2) and one from CT (Flatness), reaching a sensitivity of 100% and a specificity of 96%. Another model combining 2 PET features (IC2 and Strength), reached sensitivity of 100% and specificity of 88%, both with an undefined hazard ratio (HR) (p<0.001). The latter model obtained an accuracy of 0.91 (sensitivity 100%, specificity 81%), with a HR undefined (P = 0.023) in the testing set, however other models relying on CT radiomics features only or the combination of PET and CT features failed to validate in the testing set. Conclusion: We showed that two radiomic features derived from FDG PET were independently associated with LC in patients with NSCLC undergoing SBRT and could be combined in an accurate predictive model. This model could provide local relapse-related information and could be helpful in clinical decision-making.

Purpose: Although the incidence of de novo neuroendocrine prostate cancer (NEPC) is rare, recent data suggests that low expression of prostate-specific membrane antigen (PSMA) is associated with a spectrum of neuroendocrine (NE) hallmarks and androgen receptor (AR)-suppression in prostate cancer (PC). Previous clinical reports indicate that PCs with a phenotype similar to NE tumors can be more amenable to imaging by ¹⁸F-Fluorodeoxyglucose (FDG) rather than PSMA-targeting radioligands. In this study, we evaluated the association between NE gene signature and FDG uptake-associated genes including glucose transporters (GLUTs) and hexokinases, with the goal of providing a genomic signature to explain the reported FDG-avidity of PSMA-suppressed tumors. Methods: Data mining approaches, cell lines and patient-derived xenograft (PDX) models were used to study the levels of 14 members of the SLC2A family (encoding GLUT proteins), 4 members of the hexokinase family (genes: HK1 to 3 and GCK) and PSMA (FOLH1 gene) following AR-inhibition and in correlation with NE hallmarks. Also, we characterize a NE-like PC (NELPC) subset among a cohort of primary and metastatic PC samples with no NE histopathology. We measured glucose uptake in a NE-induced in vitro model and a zebrafish model by non-radioactive imaging of glucose uptake using fluorescent glucose bioprobe, GB2-Cy3. Results: This work demonstrates that a NE gene signature associates with differential expression of genes encoding GLUT and hexokinase proteins. In NELPC, elevated expression of GCK (encoding glucokinase protein) and decreased expression of SLC2A12 correlated with earlier biochemical recurrence. In tumors treated with AR-inhibitors, high expression of GCK and low expression of SLC2A12 correlated with NE histopathology and PSMA gene suppression. GLUT12-suppression and amplification of glucokinase was observed in NE-induced PC cell lines and PDX models. A higher glucose uptake was confirmed in low-PSMA tumors using a GB2-Cy3 probe in a zebrafish model. Conclusion: NE gene signature in NEPC and NELPC associates with a distinct transcriptional profile of GLUTs and HKs. PSMA-suppression correlates with GLUT12-suppression and glucokinase-amplification. Alteration of FDG uptake-associated genes correlated positively with higher glucose uptake in AR and PSMA-suppressed tumors. Zebrafish xenograft tumor models are an accurate and efficient pre-clinical method for monitoring non-radioactive glucose uptake.

Due to their peculiar mechanism of action, the evaluation of radiological response to immune checkpoint inhibitors (ICI) presents many challenges in solid tumors. We aimed to compare the evaluation of first response to Nivolumab by means of CT-based criteria with respect to fluorodeoxyglucose positron emission tomography (FDG-PET) response criteria in non-small-cell lung cancer (NSCLC) patients. Methods: 72 patients with advanced NSCLC were recruited in a mono-institutional ancillary trial within the expanded access program (EAP; NCT02475382) for Nivolumab. Patients underwent CT scan and FDG-PET at baseline and after 4 cycles (first evaluation). In case of progressive disease (PD), an additional evaluation was performed after two further cycles in order to confirm progression. We evaluated the response to treatment with CT scan by means of response evaluation criteria in solid tumors (RECIST) 1.1 and Immuno-related Response Criteria (IrRC) and with FDG-PET by means of PERCIST and immunotherapy-modified-PERCIST (imPERCIST) criteria. The concordance between CT- and PET-based criteria and the capability of each method to predict overall survival (OS) were evaluated. Results: 48/72 patients were evaluable for first response assessment with both PET- and CT-based criteria. We observed low concordance between CT- and PET-based criteria (Kappa value of 0.346 and 0.355 and Kappa value of 0.128 and 0.198 between PERCIST and imPERCIST versus RECIST and irRC respectively). Looking at OS, IrRC were more reliable to distinguish responders from non-responders. However thanks to the prognostic value of partial metabolic response assessed by both PERCIST and Immuno-PERCIST, PET-based response maintained prognostic significant in patients classified as progressive disease on the basis of irRC. Conclusion: Even though the present study did not support the routine use of FDG-PET in the general population of NSCLC patients treated with ICI, it suggests the added prognostic value of the metabolic response assessment, potentially improving the therapeutic decision-making.

2-Deoxy-2-[18F]fluoro-D-glucose (2-FDG) with positron emission tomography (2-FDG-PET) is undeniably useful in the clinic, among other uses, to monitor change over time using the 2-FDG standardized uptake values (SUV) metric. This report suggests some potentially serious caveats for this and related roles for 2-FDG PET. Most critical is the assumption that there is an exact proportionality between glucose metabolism and 2-FDG metabolism, called the lumped constant, LC. This report describes that LC is not constant for a specific tissue and may be variable before and after disease treatment. The purpose of this work is not to deny the clinical value of 2-FDG PET; it is a reminder that when one extends the use of an appropriately qualified imaging method, new observations may arise and further validation would be necessary. Current understanding of glucose-based energetics in vivo is based on the quantification of glucose metabolic rates with 2-FDG PET, a method that permits the non-invasive assessment in various human disorders. However, 2-FDG is only a good substrate for facilitated-glucose transporters (GLUTs) but not for sodium-dependent glucose co-transporters (SGLTs), which have recently been shown to be distributed in multiple human tissues. Thus, the GLUT-mediated in vivo glucose utilization measured by 2-FDG PET would be blinded to the potentially substantial role of functional SGLTs in glucose transport and utilization. Therefore, in these circumstances the 2-FDG LC used to quantify in vivo glucose utilization should not be expected to remain constant. 2-FDG LC variations have been especially significant in tumors, particularly at different stages of cancer development, affecting the accuracy of quantitative glucose measures and potentially limiting the prognostic value of 2-FDG, as well as its accuracy in monitoring treatments. SGLT-mediated glucose transport can be estimated using α-methyl-4-deoxy-4-[18F]fluoro-D-glucopyranoside (Me-4FDG). Utilizing both 2-FDG and Me-4FDG should provide a more complete picture of glucose utilization via both GLUT and SGLT transporters in health and disease stages. Given the widespread use of 2-FDG PET to infer glucose metabolism, appreciating the potential limitations of 2-FDG as a surrogate for glucose metabolic rate and the potential reasons for variability in LC is relevant. Even when the readout for the 2-FDG PET study is only an SUV parameter, variability in LC is important, particularly if it changes over the course of disease progression (e.g., an evolving tumor).

Introduction: A new pattern of response, so-called hyper-progressive disease (HPD), is emerging during treatment with immune checkpoint inhibitors (ICI). Our aim was to investigate the prevalence of such phenomenon and to assess its association with clinical variables and metabolic parameters by ¹⁸F-fludeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT). Methods: Data from 50 patients (34 male, 16 female, median age 73) with non-small cell lung carcinoma (NSCLC) and treated with ICI were prospectively collected. All patients underwent contrast-enhanced CT, ¹⁸F-FDG PET/CT, and complete peripheral blood sample at baseline before ICI. HPD was defined according to clinical and radiologic criteria. Because of the rapid disease progression or worsening of clinic conditions, radiologic response assessment was available for 46 patients. OS were analyzed using the Kaplan–Meier method and the log-rank test. A Cox proportional hazards regression analysis was used to evaluate factors independently associated with OS. Median follow-up was 12.4 months (9.7-15.2 months). Results: We identified the following response categories: 10 cases as complete/partial response (CR/PR), 17 cases with stable disease (SD), 5 patients with progressive disease (PD), and 14 with HPD. Among metabolic parameters we observed a statistically significant association between HPD status and tumor burden, expressed by both MTV (756.1ml for HPD vs 475.6ml for non-HPD, P = 0.011) and TLG (287.3 for HPD vs 62.1 for non-HPD, P = 0.042). Among clinical variables, 12/14 patients (85.7%) within the HPD group compared with 8/32 patients (25%) in the non-HDP group had more than two metastatic sites (p<0.001). In addition, the derived neutrophil-to-lymphocyte ratio (dNLR) and platelet counts was significantly associated with HPD status (P = 0.038, P = 0.025, respectively). Survival analysis showed a median OS of 4 months for HPD group compared with 15 months within non-HPD patients (P = 0.003). Likewise, median OS was significantly different when we considered all the response categories: CR/PR, SD, PD, and HPD (P = 0.001). Finally, Multivariate analysis identified MTV and dNLR as independent predictors for OS. Conclusion: Our results suggest that the use of ICI might represent a concern in patients with high metabolic tumor burden and inflammatory indexes at baseline. However Additional studies are needed.

Rationale: The presence of metastasis in local lymph nodes (LNs) is a key factor influencing choice of therapy and prognosis in cervical and endometrial cancers; therefore, the exploration of sentinel LNs (SLNs) is highly important. Currently, however, SLN mapping requires LN biopsy for pathologic evaluation, since there are no clinical imaging approaches that can identify tumor-positive LNs in early stages. Staging lymphadenectomy poses risks, such as leg lymphedema or lymphocyst formation. Furthermore, in 80% to 90% of patients, the explored LNs are ultimately tumor free, meaning the vast majority of patients are unnecessarily subjected to lymphadenectomy. Methods: Current lymphoscintigraphy methods only identify the anatomic location of the SLNs but do not provide information on their tumor status. There are no non-invasive methods to reliably identify metastases in LNs before surgery. We have developed positron lymphography (PLG), a method to detect tumor-positive LNs, where ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) is injected interstitially into the uterine cervix the day of surgery, and its rapid transport through the lymphatic vessels to the SLN is then visualized with dynamic positron emission tomography/computed tomography (PET/CT). We previously showed that PLG was able to identify metastatic LNs in animal models. Here, we present the first results from our pilot clinical trial (clinical trials identifier NCT02285192) in 23 patients with uterine or cervical cancer. On the morning of surgery, ¹⁸F-FDG was injected into the cervix, followed by an immediate dynamic PET/CT scan of the pelvis and a delayed 1-h whole body scan. Results: There were 3 (15%) node-positive cases on final pathologic analysis, and all LNs (including one with a focus of only 80 tumor cells) were identified by PLG except one node with an 11-mm micrometastasis. There were 2 (10%) false-positive cases with PLG, in which final pathology of the corresponding SLNs was negative for tumor. Methods: Current lymphoscintigraphy methods only identify the anatomic location of the SLNs but do not provide information on their tumor status. There are no non-invasive methods to reliably identify metastases in LNs before surgery. We have developed positron lymphography (PLG), a method to detect tumor-positive LNs, where ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) is injected interstitially into the uterine cervix the day of surgery, and its rapid transport through the lymphatic vessels to the SLN is then visualized with dynamic positron emission tomography/computed tomography (PET/CT). We previously showed that PLG was able to identify metastatic LNs in animal models. Here, we present the first results from our pilot clinical trial (clinical trials identifier NCT02285192) in 23 patients with uterine or cervical cancer. On the morning of surgery, ¹⁸F-FDG was injected into the cervix, followed by an immediate dynamic PET/CT scan of the pelvis and a delayed 1-h whole body scan. Results: There were 3 (15%) node-positive cases on final pathologic analysis, and all LNs (including one with a focus of only 80 tumor cells) were identified by PLG, except for one node with an 11-mm micrometastasis. There were 2 (10%) false-positive cases with PLG, in which final pathology of the corresponding SLNs was negative for tumor. Conclusion: This first-in-human study of PLG in women with uterine and cervical cancer demonstrates its feasibility and its ability to identify patients with nodal metastases, and warrants further evaluation in additional studies.

We aimed to evaluate the diagnostic performance of ¹⁸F-FDG PET/CT for the detection of post-transplantation lymphoproliferative disorder (PTLD) in a pediatric population and explore its feasibility during response assessment. Methods: This retrospective study included 28 pediatric transplant recipients who underwent a total of 32 ¹⁸F-FDG PET/CT scans due to clinical suspicion of PTLD within an 8-year period. Pathology reports and 2-year follow-up were used as reference standard. Twenty-one response assessment ¹⁸F-FDG PET/CT scans were re-evaluated according to the Lugano criteria. Results: The diagnosis of PTLD was established in 14 patients (49%). Sensitivity, specificity, positive predictive value, and negative predictive value of ¹⁸F-FDG PET/CT for the detection of PTLD in children with a clinical suspicion of this disease, was 50% (7/14), 100% (18/18), 100% (7/7), and 72% (18/25), respectively. False-negative results occurred in patients with PTLD in the Waldeyer’s ring, cervical lymph nodes or small bowel with either non-destructive or polymorphic PTLD. Two of 5 interim ¹⁸F-FDG PET/CT scans and 3 of 9 end-of-treatment ¹⁸F-FDG PET/CT scans were false-positive. Conclusion: ¹⁸F-FDG PET/CT had good specificity and positive predictive value but low to moderate sensitivity and negative predictive value for the detection of PTLD in a 28 pediatric patient cohort with a clinical suspicion of this disease. False-negative results were confirmed in the Waldeyer’s ring, cervical lymph nodes and small bowel with either non-destructive or polymorphic PTLD subtypes. ¹⁸F-FDG PET/CT appears to have a limited role in the response assessment setting of pediatric PTLD, given the observed high proportions of false-positives both at interim and end-of-treatment evaluations.

Introduction: To use positron emission tomography coupled with computed tomography (¹⁸FDG-PET/CT) to identify a high-risk subgroup requiring therapeutic intensification among patients with locally advanced cervical cancer (LACC) and para-aortic lymph node (PALN) involvement. Methods: In this retrospective multicentric study, patients with LACC and PALN involvement concurrently treated with chemoradiotherapy and extended-field radiotherapy (EFR) between 2006 and 2016 were included. A senior nuclear medicine specialist in PET for gynaecologic oncology reviewed all ¹⁸FDG-PET/CT scans. Metabolic parameters including maximum standardised uptake value (SUV_max), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were determined for the primary tumour, pelvic lymph nodes and PALN. Associations between these parameters and overall survival (OS) were assessed with Cox's proportional hazards model. Results: Sixty-eight patients were enrolled in the study. Three-year OS was 55.5% (95% CI (40.8-68.0)). When adjusted for age, stage and histology, pelvic lymph node TLG, PALN TLG and PALN SUV_max were significantly associated with OS (p<0.005). Conclusion: FDG-PET/CT was able to identify predictors of survival in the homogeneous subgroup of patients with LACC and PALN involvement, thus allowing therapeutic intensification to be proposed.

The objective of this retrospective study was to determine the role of ¹⁸F-FDG PET/CT in a large cohort of 495 patients with metastatic neuroendocrine neoplasms (NENs) who were treated with peptide receptor radionuclide therapy (PRRT) with a long-term follow-up. Methods: The 495 patients were treated with ¹⁷⁷Lu- and/or ⁹⁰Y- DOTATOC/DOTATATE PRRT between 2/2002 and 7/2018. All subjects received both ⁶⁸Ga-DOTATOC/TATE/NOC and ¹⁸F-FDG PET/CT prior to treatment and were followed 3-189 months. Kaplan-Meier analysis, log-rank test (Mantel-Cox), and Cox regression analysis were performed for overall survival (OS) and progression-free survival (PFS). Results: 199 patients (40.2%) presented with pancreatic NEN, 49 with CUP (cancer of unknown primary), 139 with midgut NEN, whereas the primary tumor was present in the rectum in 20, in the lung in 38, in the stomach in 8 and other locations in 42 patients. FDG-PET/CT was positive in 382 (77.2%) patients and 113 (22.8%) were FDG-negative before PRRT, while 100% were ⁶⁸Ga-DOTATOC/TATE/NOC positive. For all patients, the median PFS and OS, defined from start of PRRT, were 19.6 mo and 58.7 mo, respectively. Positive FDG predicted shorter PFS (18.5 mo vs 24.1 mo; P = 0.0015) and OS (53.2 mo vs 83.1 mo; P < 0.001) than negative FDG. Amongst the pancreatic NEN, the median OS was 52.8 mo in FDG positive and 114.3 mo in FDG negative subjects (P = 0.0006). For all patients with positive ¹⁸F-FDG uptake, and a ratio of the highest SUV_max on ⁶⁸Ga-SSTR PET to the most ¹⁸F-FDG-avid tumor lesions >2, the median OS was 53.0 mo, compared to 43.4 mo in those patients with a ratio <2 (P = 0.030). For patients with no ¹⁸F-FDG uptake (complete "mismatch" imaging pattern), the median OS was 108.3 mo vs 76.9 mo for SUV_max >15.0 and ≤15.0 on ⁶⁸Ga-SSTR PET/CT, respectively. Conclusion: The presence of positive lesions on ¹⁸F-FDG PET is an independent prognostic factor in patients with NEN treated with PRRT. Metabolic imaging with ¹⁸F-FDG PET/CT compliments the molecular imaging aspect of ⁶⁸Ga-SSTR PET/CT for the prognosis of survival after PRRT. High SSTR expression combined with negative ¹⁸F-FDG PET/CT imaging is associated with the most favorable long-term prognosis.

A data-driven method for respiratory gating in PET has recently been commercially developed. We sought to compare the performance of the algorithm to an external, device-based system for oncological [¹⁸F]-FDG PET/CT imaging. Methods: 144 whole-body [¹⁸F]-FDG PET/CT examinations were acquired using a Discovery D690 or D710 PET/CT scanner (GE Healthcare), with a respiratory gating waveform recorded by an external, device based respiratory gating system. In each examination, two of the bed positions covering the liver and lung bases were acquired with duration of 6 minutes. Quiescent period gating retaining ~50% of coincidences was then able to produce images with an effective duration of 3 minutes for these two bed positions, matching the other bed positions. For each exam, 4 reconstructions were performed and compared: data driven gating (DDG-retro), external device-based gating (RPM Gated), no gating but using only the first 3 minutes of data (Ungated Matched), and no gating retaining all coincidences (Ungated Full). Lesions in the images were quantified and image quality was scored by a radiologist, blinded to the method of data processing. Results: The use of DDG-retro was found to increase SUVmax and to decrease the threshold-defined lesion volume in comparison to each of the other reconstruction options. Compared to RPM-gated, DDG-retro gave an average increase in SUV_max of 0.66 ± 0.1 g/mL (n=87, p<0.0005). Although results from the blinded image evaluation were most commonly equivalent, DDG-retro was preferred over RPM gated in 13% of exams while the opposite occurred in just 2% of exams. This was a significant preference for DDG-retro (p=0.008, n=121). Liver lesions were identified in 23 exams. Considering this subset of data, DDG-retro was ranked superior to Ungated Full in 6/23 (26%) of cases. Gated reconstruction using the external device failed in 16% of exams, while DDG-retro always provided a clinically acceptable image. Conclusion: In this clinical evaluation, the data driven respiratory gating technique provided superior performance as compared to the external device-based system. For the majority of exams the performance was equivalent, but data driven respiratory gating had superior performance in 13% of exams, leading to a significant preference overall.

Cancer Survival is related to tumor volume. FDG PET measurement of tumor volume holds promise but is not yet a clinical tool. Measurements come in two forms: the total lesion volume (TLV) based on the number of voxels in the tumor and secondly the total lesion glycolysis (TLG) which is the TLV multiplied by the average SUL per voxel of the tumor (SUL is the standardize uptake value normalized for lean mass). In this study we measured tumor volume in patients with malignant pleural mesothelioma (MPM). METHODS: A threshold-based program in IDL was developed to measure tumor volume in FDG PET images. 19 patients with malignant pleural mesothelioma (MPM) were studied before and after two cycles (6 weeks) of chemo-immunotherapy. Measurements included the total lesion volume (TLV), Total Lesion Glycolysis (TLG), the sum of the SULs in the tumor (SUL- total), a measure of total FDG uptake, and the average SUL per voxel. RESULTS: Baseline MPM volumes (TLV) ranged from 11 to 2610 cc. TLG values ranged from 32 to 8552 SUL-cc and were strongly correlated with TLV. While tumor volumes ranged over 3 orders of magnitude, the average SUL per voxel, SUL-average, stayed within a narrow range of 2.4 to 5.3 units. Thus, TLV was the major component of TLG while SUL-average was a minor component and was essentially constant. Further evaluation of SUL-average showed that in this cohort it’s two components SUL-total and tumor volume changed in parallel and were strongly correlated, r= 0.99, p<.01. Thus, whether the tumors were large or small, the FDG uptake as measured by SUL-total was proportional to the total tumor volume. Conclusion: TLG equals TLV multiplied by the average SUL per voxel, essentially TLV multiplied by a constant. Thus TLG, commonly considered a measure of "metabolic activity" in tumors, is also in this cohort a measure of tumor volume. The constancy of SUL per voxel is due to FDG uptake being proportional to tumor volume. Thus, in this study, the FDG uptake was also a measure of volume.

Intravenous access is difficult in some patients referred for ¹⁸F-FDG PET imaging. Extravasation at the injection site and accumulation in central catheters can lead to limited tumor ¹⁸F-FDG uptake, erroneous quantitation, and significant image artifacts. In this study, we compared the human biodistribution and dosimetry for ¹⁸F-FDG after oral and intravenous administrations sequentially in the same subjects to ascertain the dosimetry and potential suitability of orally administered ¹⁸F-FDG as an alternative to intravenous administration. We also compared our detailed intravenous ¹⁸F-FDG dosimetry with older dosimetry data. Methods: Nine healthy volunteers (6 male and 3 female; aged 19–32 y) underwent PET/CT imaging after oral and intravenous administration of ¹⁸F-FDG. Identical preparation and imaging protocols (except administration route) were used for oral and intravenous studies. During each imaging session, 9 whole-body PET scans were obtained at 5, 10, 20, 30, 40, 50, 60, 120, and 240 min after ¹⁸F-FDG administration (370 ± 16 MBq). Source organ contours drawn using CT were overlaid onto registered PET images to extract time–activity curves. Time-integrated activity coefficients derived from time–activity curves were given as input to OLINDA/EXM for dose calculations. Results: Blood uptake after orally administered ¹⁸F-FDG peaked at 45–50 min after ingestion. The oral-to-intravenous ratios of ¹⁸F-FDG uptake for major organs at 45 min were 1.07 ± 0.24 for blood, 0.94 ± 0.39 for heart wall, 0.47 ± 0.12 for brain, 1.25 ± 0.18 for liver, and 0.84 ± 0.24 for kidneys. The highest organ-absorbed doses (μGy/MBq) after oral ¹⁸F-FDG administration were observed for urinary bladder (75.9 ± 17.2), stomach (48.4 ± 14.3), and brain (29.4 ± 5.1), and the effective dose was significantly higher (20%) than after intravenous administration (P = 0.002). Conclusion: ¹⁸F-FDG has excellent bioavailability after oral administration, but peak organ activities occur later than after intravenous injection. These data suggest PET at 2 h after oral ¹⁸F-FDG administration should yield images that are comparable in biodistribution to conventional clinical images acquired 1 h after injection. Oral ¹⁸F-FDG is a palatable alternative to intravenous ¹⁸F-FDG when venous access is problematic.

The present study examined the predictive values of amyloid PET, ¹⁸F-FDG PET, and nonimaging predictors (alone and in combination) for development of Alzheimer dementia (AD) in a large population of patients with mild cognitive impairment (MCI). Methods: The study included 319 patients with MCI from the Alzheimer Disease Neuroimaging Initiative database. In a derivation dataset (n = 159), the following Cox proportional-hazards models were constructed, each adjusted for age and sex: amyloid PET using ¹⁸F-florbetapir (pattern expression score of an amyloid-β AD conversion–related pattern, constructed by principle-components analysis); ¹⁸F-FDG PET (pattern expression score of a previously defined ¹⁸F-FDG–based AD conversion–related pattern, constructed by principle-components analysis); nonimaging (functional activities questionnaire, apolipoprotein E, and mini-mental state examination score); ¹⁸F-FDG PET + amyloid PET; amyloid PET + nonimaging; ¹⁸F-FDG PET + nonimaging; and amyloid PET + ¹⁸F-FDG PET + nonimaging. In a second step, the results of Cox regressions were applied to a validation dataset (n = 160) to stratify subjects according to the predicted conversion risk. Results: On the basis of the independent validation dataset, the ¹⁸F-FDG PET model yielded a significantly higher predictive value than the amyloid PET model. However, both were inferior to the nonimaging model and were significantly improved by the addition of nonimaging variables. The best prediction accuracy was reached by combining ¹⁸F-FDG PET, amyloid PET, and nonimaging variables. The combined model yielded 5-y free-of-conversion rates of 100%, 64%, and 24% for the low-, medium- and high-risk groups, respectively. Conclusion: ¹⁸F-FDG PET, amyloid PET, and nonimaging variables represent complementary predictors of conversion from MCI to AD. Especially in combination, they enable an accurate stratification of patients according to their conversion risks, which is of great interest for patient care and clinical trials.

With high sensitivity in detecting acute brain events such as seizures, FDG PET can be used as an important tool for neurocutaneous melanosis disease monitoring.

The first Biograph Vision PET/CT system (Siemens Healthineers) was installed at the University Medical Center Groningen. Improved performance of this system could allow for a reduction in activity administration or scan duration. This study evaluated the effects of reduced scan duration in oncologic ¹⁸F-FDG PET imaging on quantitative and subjective imaging parameters and its influence on clinical image interpretation. Methods: Patients referred for a clinical PET/CT scan were enrolled in this study, received a weight-based ¹⁸F-FDG injected activity, and underwent list-mode PET acquisition at 180 s per bed position (s/bp). Acquired PET data were reconstructed using the vendor-recommended clinical reconstruction protocol (hereafter referred to as "clinical"), using the clinical protocol with additional 2-mm gaussian filtering (hereafter referred to as "clinical+G2"), and—in conformance with European Association of Nuclear Medicine Research Ltd. (EARL) specifications—using different scan durations per bed position (180, 120, 60, 30, and 10 s). Reconstructed images were quantitatively assessed for comparison of SUVs and noise. In addition, clinically reconstructed images were qualitatively evaluated by 3 nuclear medicine physicians. Results: In total, 30 oncologic patients (22 men, 8 women; age: 48–88 y [range], 67 ± 9.6 y [mean ± SD]) received a single weight-based (3 MBq/kg) ¹⁸F-FDG injected activity (weight: 45–123 kg [range], 81 ± 15 kg [mean ± SD]; activity: 135–380 MBq [range], 241 ± 47.3 MBq [mean ± SD]). Significant differences in lesion SUV_max were found between the 180-s/bp images and the 30- and 10-s/bp images reconstructed using the clinical protocols, whereas no differences were found in lesion SUV_peak. EARL-compliant images did not show differences in lesion SUV_max or SUV_peak between scan durations. Quantitative parameters showed minimal deviation (~5%) in the 60-s/bp images. Therefore, further subjective image quality assessment was conducted using the 60-s/bp images. Qualitative assessment revealed the influence of personal preference on physicians’ willingness to adopt the 60-s/bp images in clinical practice. Although quantitative PET parameters differed minimally, an increase in noise was observed. Conclusion: With the Biograph Vision PET/CT system for oncologic ¹⁸F-FDG imaging, scan duration or activity administration could be reduced by a factor of 3 or more with the use of the clinical+G2 or the EARL-compliant reconstruction protocol.

C-X-C motif chemokine receptor 4 (CXCR4) is expressed on the surface of various cell types involved in atherosclerosis, with a particularly rich receptor expression on macrophages and T cells. First pilot studies with ⁶⁸Ga-pentixafor, a novel CXCR4-directed PET tracer, have shown promise to noninvasively image inflammation within atherosclerotic plaques. The aim of this retrospective study was to investigate the performance of ⁶⁸Ga-pentixafor PET/CT for imaging atherosclerosis in comparison to ¹⁸F-FDG PET/CT. Methods: Ninety-two patients (37 women and 55 men; mean age, 62 ± 10 y) underwent ⁶⁸Ga-pentixafor and ¹⁸F-FDG PET/CT for staging of oncologic diseases. In these subjects, lesions in the walls of large arteries were identified using morphologic and PET criteria for atherosclerosis (n = 652). Tracer uptake was measured and adjusted for vascular lumen (background) signal by calculation of target-to-background ratios (TBRs) by 2 investigators masked to the other PET scan. On a lesion-to-lesion and patient basis, the TBRs of both PET tracers were compared and additionally correlated to the degree of arterial calcification as quantified in CT. Results: On a lesion-to-lesion basis, ⁶⁸Ga-pentixafor and ¹⁸F-FDG uptake showed a weak correlation (r = 0.28; P < 0.01). ⁶⁸Ga-pentixafor PET identified more lesions (n = 290; TBR ≥ 1.6, P < 0.01) and demonstrated higher uptake than ¹⁸F-FDG PET (1.8 ± 0.5 vs. 1.4 ± 0.4; P < 0.01). The degree of plaque calcification correlated negatively with both ⁶⁸Ga-pentixafor and ¹⁸F-FDG uptake (r = –0.38 vs. –0.31, both P < 0.00001). Conclusion: CXCR4-directed imaging of the arterial wall with ⁶⁸Ga-pentixafor PET/CT identified more lesions than ¹⁸F-FDG PET/CT, with only a weak correlation between tracers. Further studies to elucidate the underlying biologic mechanisms and sources of CXCR4 positivity, and to investigate the clinical utility of chemokine receptor–directed imaging of atherosclerosis, are highly warranted.

Monoclonal antibodies (mAbs) against programmed cell death 1 (PD-1), such as nivolumab and pembrolizumab, are associated with high response rates in patients with relapsed or refractory classic Hodgkin lymphoma (HL). To date, no prognostic factor for overall survival (OS) has been established with these agents in HL. We examined whether the first early response assessment evaluated using ¹⁸F-FDG PET/CT may be associated with OS in this setting. Methods: This retrospective study included 45 patients from 34 institutions. In a masked, centralized review, 3 independent radiologists classified PET/CT scans obtained at a median of 2.0 mo (interquartile range, 1.7–3.7 mo) after nivolumab initiation using existing criteria (i.e., 2014 Lugano classification and 2016 LYRIC). Patients were classified according to 4 possible response categories: complete metabolic response (CMR), partial metabolic response (PMR), no metabolic response (NMR), or progressive metabolic disease (PMD). Because the OS of patients with NMR and PMR was similar, they were grouped together. OS was estimated using the Kaplan–Meier method and compared between groups using log-rank testing. Results: Eleven patients (24%) died after a median follow-up of 21.2 mo. The classification was identical between Lugano and LYRIC because all 16 progression events classified as indeterminate response per LYRIC were confirmed on subsequent evaluations. Both Lugano and LYRIC classified patients as CMR in 13 cases (29%), PMD in 16 (36%), NMR in 4 (9%), and PMR in 12 (27%). The 2-y OS probability was significantly different in patients with PMD (0.53; 95% confidence interval [95%CI], 0.32–0.87), NMR or PMR (0.80; 95%CI, 0.63–1.00), and CMR (1.00; 95%CI, 1.00–1.00) in the overall population (P = 0.02, 45 patients), as well as according to a landmark analysis at 3 mo (P = 0.05, 32 patients). Conclusion: In relapsed or refractory HL patients treated with anti-PD-1 mAbs, the first early PET/CT assessment using either Lugano or LYRIC predicted OS and allowed early risk stratification, suggesting that PET/CT might be used to develop risk-adapted strategies.

This study showed that treatment with a therapeutic monoclonal immunoglobulin-G1 antibody against phosphorylcholine on oxidized phospholipids preserves coronary flow reserve and attenuates atherosclerotic inflammation as determined by the uptake of ¹⁸F-fluorodeoxyglucose in atherosclerotic mice. The noninvasive imaging techniques represent translational tools to assess the efficacy of phosphorylcholine-targeted therapy on coronary artery function and atherosclerosis in clinical studies.