Development of a Visually Calculated SUVmean (HIT Score) on Screening PSMA PET/CT to Predict Treatment Response to 177Lu-PSMA Therapy: Comparison with Quantitative SUVmean and Patient Outcomes.

177Lu-PSMA therapy is an effective treatment in patients with metastatic castration-resistant prostate cancer. SUVmean is a valuable screening biomarker to assess the suitability for 177Lu-PSMA therapy but requires quantitative software. This study aims to develop a simple, clinically applicable prostate-specific membrane antigen PET/CT score that encompasses the elements of SUVmean without requiring additional quantification. Methods: Datasets from ethics-approved trials of patients with metastatic castration-resistant prostate cancer after androgen receptor signaling inhibition and taxane chemotherapy (or unfit for taxane), who were treated with 177Lu-PSMA-617 and 177Lu-PSMA I&T with a pretreatment screening with 68Ga-PSMA-11 PET/CT, and clinical outcome data, including a prostate-specific antigen (PSA) 50% response rate (PSA50), PSA progression-free survival (PSA-PFS), and overall survival (OS), were included. The screening 68Ga-PSMA-11 PET/CT of all participants was analyzed both semiquantitatively and visually. Semiquantitative analysis was used to derive the SUVmean Visual analysis of the 68Ga-PSMA-11 PET/CT images involved a binary visual heterogeneity assessment (homogeneous or heterogeneous), allocating a tumor SUVmax range (<15, 15-29, 30-49, 50-79, or ≥80). A 4-category score incorporating both heterogeneity and intensity of tumors (HIT) was then developed as a combination of heterogeneity and intensity (SUVmax range). The SUVmax was less than 15 for score 1, 15-79 with heterogeneous intensity for score 2, 15-79 with homogeneous intensity for score 3, and 80 or greater for score 4. This score was evaluated according to clinical outcomes (PSA50, PSA-PFS, and OS) and compared with SUVmean Results: Data from 139 participants were analyzed. In total, 75 (54%) patients achieved a PSA50 with a median PSA-PFS of 5.5 mo (95% CI, 4.1-6.0 mo) and an OS of 13.5 mo (95% CI, 11.1-17.9 mo). SUVmean was associated with PSA50 and survival outcomes when analyzed as a continuous variable or as quartiles. The PSA50 for HIT scores 1-4 was 0%, 39%, 65%, and 76%, respectively. The HIT score was strongly related to PSA-PFS and OS (log-rank test, P < 0.001 and P = 0.002). The median PSA-PFS for HIT scores 1-4 was 1.0, 4.1, 6.0, and 8.5, respectively, and the median OS was 7.6, 12.0, 18.5, and 16.9 mo, respectively. Cohen κ between readers for the HIT score was 0.71. Conclusion: A prostate-specific membrane antigen PET/CT score incorporating HIT derived from tools on a standard PET workstation is comparable with quantitative SUVmean as a prognostic tool following 177Lu-PSMA therapy.

Patient outcomes following a response biomarker-guided approach to treatment using 177Lu-PSMA-I&T in men with metastatic castrate-resistant prostate cancer (Re-SPECT).

Background: 177LuPSMA is an effective treatment in metastatic castrate-resistant prostate cancer with trials adopting a standardised dose interval. Adjusting treatment intervals utilising early response biomarkers may improve patient outcomes. Objective: This study evaluated progression-free survival (PFS) and overall survival (OS) based on treatment interval adjustment utilising 177LuPSMA 24-h SPECT/CT (177Lu-SPECT) and early prostate-specific antigen (PSA) response. Design: Retrospective analysis of a clinical 177Lu-PSMA-I&T treatment programme. Methods: In all, 125 men were treated with 6-weekly 177LuPSMA-I&T [median 3 cycles, interquartile range (IQR): 2-4], median dose 8.0 GBq [95% confidence interval (CI): 7.5-8.0]. Imaging screening involved 68GaPSMA-11 PET/diagnostic CT. 177Lu-SPECT/diagnostic CT was acquired following each therapy, and clinical assessments 3-weekly. Following dose 2 (week 6), a composite PSA and 177Lu-SPECT/CT imaging response [partial response (PR), stable disease (SD), and progressive disease (PD)] determined ongoing management. Response group (RG) 1 (marked reduction in PSA/imaging PR) break in treatment until subsequent PSA rise, then re-treatment. RG 2 (stable or reduced PSA and/or imaging SD) 6-weekly treatments until six doses, or no longer clinically benefitting. RG 3 (rise in PSA and/or imaging PD) recommended for an alternative treatment. Results: Overall PSA50% response rate (PSARR) was 60% (75/125), median PSA-PFS 6.1 months (95%CI: 5.5-6.7), and median OS 16.8 months (95%CI: 13.5-20.1). 35% (41/116) were classified as RG 1, 34% (39/116) RG 2, and 31% (36/116) RG 3. PSARRs by RG were 95% (38/41), 74% (29/39), and 8% (3/36); median PSA-PFS rates were 12.1 months (95%CI: 9.3-17.4), 6.1 months (95%CI: 5.8-9.0), and 2.6 months (95%CI: 1.6-3.1); and OS rates were 19.2 months (95%CI: 16.8-20.7), 13.2 months (95%CI: 12.0-18.8), and 11.2 months (95%CI: 8.7-15.6) for RG 1, 2, and 3, respectively. The median months of 'treatment holiday' for RG 1 was 6.1 months (IQR: 3.4-8.7). Nine men had received prior 177LuPSMA-617 and were retreated with 177LuPSMA-I&T, with a PSARR of 56% on re-treatment. Conclusion: Personalising dosing regimens using early response biomarkers with 177LuPSMA has the potential to achieve similar treatment responses to continuous dosing while allowing treatment breaks or intensification. Further evaluation of early response biomarker-guided treatment regimens in prospective trials is warranted. Plain Language Summary: Lutetium-PSMA therapy is a new therapy for metastatic prostate cancer that is well tolerated and effective. However, not all men respond equally, with some responding very well and others progressing early. Personalising treatments require tools that can accurately measure treatment responses, preferably early in the treatment course, so adjustments to treatment can be made. Lutetium-PSMA can measure tumour sites after each therapy by taking whole body 3D images at 24 h using a small radiation wave from the treatment itself. This is called a SPECT scan. Previous work has shown that both prostate-specific antigen (PSA) response and changes in tumour volume on a SPECT scan can predict how patients will respond to treatment as early as dose 2. This study demonstrates that stratifying how men are treated based on the results of the 6-week SPECT scan and PSA response potentially allows a third of men to have break in treatment and that these men have both longer time to disease progression and OS. Men with an increase in tumour volume and increase in PSA early in treatment (6 weeks) had shorter time to disease progression and OS. Men with early biomarker disease progression were offered alternative treatments early in an attempt to allow the opportunity to allow a more effective potential therapy, if one was available. The study is an analysis of a clinical programme, and was not a prospective trial. As such, there are potential biases that could influence results. Hence, while the study is encouraging for the use of early response biomarkers to guide better treatment decisions, this must be validated in a well-designed clinical trial.

177Lu-PSMA SPECT Quantitation at 6 Weeks (Dose 2) Predicts Short Progression-Free Survival for Patients Undergoing 177Lu-PSMA-I&T Therapy.

177Lu-PSMA is an effective treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and adjust treatment may be improved using predictive tools. This study aimed to evaluate change in 177Lu-PSMA SPECT quantitative parameters to monitor treatment response. Methods: One hundred twenty-seven men with progressive mCRPC previously treated with androgen-signaling inhibition (99%) and chemotherapy (71%) received a median of 3 (interquartile range [IQR], 2-5) 8-GBq (IQR, 8-8.5 GBq) doses of 177Lu-PSMA-I&T. Imaging included 68Ga-PSMA-11 PET/CT (SUVmax > 15 at a single site and > 10 at all sites > 2 cm), diagnostic CT, and 177Lu SPECT/CT from vertex to mid thigh (24 h after treatment). 177Lu SPECT/CT quantitative analysis was undertaken at cycles 1 (baseline) and 2 (week 6) of treatment. Clinical and biochemical results were assessed to evaluate prostate-specific antigen (PSA) progression-free survival (PFS) and overall survival (OS). Results: A PSA reduction of more than 50% was seen in 58% (74/127). The median PSA PFS was 6.1 mo (95% CI, 5.5-6.7), and OS was 16.8 mo (95% CI, 13.5-20.1). At the time of analysis, 41% (52/127) were deceased. At baseline and week 6, 76% (96/127) had analyzable serial 177Lu SPECT/CT imaging. SPECT total tumor volume (TTV) was reduced between baseline and week 6 in 74% (71/96; median, -193; IQR, -486 to -41). Any increase in SPECT TTV between baseline and week 6 was associated with significantly shorter PSA PFS (hazard ratio, 2.5; 95% CI, 1.5-4.2; P = 0.0008) but not OS. Median PSA PFS in those with an increase in SPECT TTV was 3.7 mo (95% CI, 2.8-6.8), compared with 6.7 mo (95% CI, 5.8-10.6) in those with no increase in SPECT TTV. An increase in SPECT TTV greater than 20% was also associated with PSA PFS (hazard ratio, 1.9; 95% CI, 1.2-3.0; P = 0.008) but less significantly than any change in SPECT TTV. There was a significant difference in PSA PFS between patients with both increased PSA and SPECT TTV and patients with reduced SPECT TTV and PSA (median, 2.8 vs. 9.0 mo; P < 0.0001). Conclusion: Increasing PSMA SPECT TTV on quantitative 177Lu SPECT/CT predicts short progression-free survival and may play a future role as an imaging response biomarker, identifying when to cease or intensify 177Lu-PSMA therapy.

Evaluation of 177Lu-PSMA-617 SPECT/CT Quantitation as a Response Biomarker Within a Prospective 177Lu-PSMA-617 and NOX66 Combination Trial (LuPIN).

177Lu-PSMA-617 is an effective and novel treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and therefore efficacy may be improved using predictive tools. This study investigated the predictive value of serial 177Lu-PSMA-617 SPECT/CT (177Lu SPECT) imaging in monitoring treatment response. Methods: Fifty-six men with progressive mCRPC previously treated with chemotherapy and novel androgen signaling inhibitor were enrolled into the LuPIN trial and received up to 6 doses of 177Lu-PSMA-617 and a radiation sensitizer (3-(4-hydroxyphenyl)-2H-1-benzopyran-7-ol [NOX66]). 68Ga-PSMA-11 and 18F-FDG PET/CT were performed at study entry and exit, and 177Lu SPECT from vertex to mid thighs was performed 24 h after each treatment. SPECT quantitative analysis was undertaken at cycles 1 (baseline) and 3 (week 12) of treatment. Results: Thirty-two of the 56 men had analyzable serial 177Lu SPECT imaging at both cycle 1 and cycle 3. In this subgroup, median prostate-specific antigen (PSA) progression-free survival (PFS) was 6.3 mo (95% CI, 5-10 mo) and median overall survival was 12.3 mo (95% CI, 12-24 mo). The PSA 50% response rate was 63% (20/32). 177Lu SPECT total tumor volume (SPECT TTV) was reduced in 68% (22/32; median, -0.20 m3 [95% CI, -1.4 to -0.001]) and increased in 31% (10/32; median, 0.36 [95% CI, 0.1-1.4]). Any increase in SPECT TTV was associated with shorter PSA PFS (hazard ratio, 4.1 [95% CI, 1.5-11.2]; P = 0.006). An increase of 30% or more in SPECT TTV was also associated with a shorter PSA PFS (hazard ratio, 3.3 [95% CI, 1.3-8.6]; P =0.02). Tumoral SUVmax was reduced in 91% (29/32) and SUVmean in 84% (27/32); neither was associated with PSA PFS or overall survival outcomes. PSA progression by week 12 was also associated with a shorter PSA PFS (hazard ratio, 26.5 [95% CI, 5.4-131]). In the patients with SPECT TTV progression at week 12, 50% (5/10) had no concurrent PSA progression (median PSA PFS, 4.5 mo [95% CI, 2.8-5.6 mo]), and 5 of 10 men had both PSA and SPECT TTV progression at week 12 (median PSA PFS, 2.8 mo [95% CI, 1.8-3.7 mo]). Conclusion: Increasing SPECT TTV on quantitative 177Lu SPECT predicts a short PFS and may play a future role as an imaging response biomarker.

Diagnostic value of 68 Ga-DOTATATE PET-CT imaging for staging of ER+ /PR+ HER2- breast cancer patients with metastatic disease: Comparison with conventional imaging with bone scan, diagnostic CT and 18 F-FDG PET-CT in a prospective pilot trial.

INTRODUCTION: 18 F-Fludeoxyglucose PET-CT (FDG) is increasingly used to stage breast cancer. Most breast cancers express the Oestrogen Receptor (ER) and Progesterone Receptor (PR), and this subtype demonstrates lower activity on FDG imaging. Somatostatin receptors (SSTR) offer a potentially improved radiotracer target for ER+ /PR+ breast cancer. We present the first in vivo clinical study comparing 68 Ga-DOTATATE PET-CT (DOTA) to FDG and conventional imaging (bone scan and diagnostic CT), in metastatic ER+ /PR+ human epidermal growth factor receptor 2 (HER2) negative breast cancer. METHODS: Patients with clinically progressive metastatic ER+ /PR+ HER2- breast cancer underwent restaging with DOTA, FDG and conventional imaging. Scans were analysed visually, and semi-quantitatively. Wilcoxon-Rank Scoring was used to assess significance. RESULTS: Ten women (mean age 57 years) underwent imaging. 8/10 demonstrated disease on both DOTA and FDG. 2/10 positive on conventional imaging, but DOTA- /FDG- , and had no disease progression at 1-year follow-up. Heterogeneity of uptake was seen between DOTA and FDG with 5 bone lesions DOTA+ /FDG- and 1 bone lesion FDG+ /DOTA- . Twenty-one visceral lesions were FDG+ /DOTA- (2 patients), with 10/21 identified on conventional imaging. Maximum standard uptake values (SUV max) of DOTA were greater than FDG (10.9 vs. 6.6, P = ns). Four sites were biopsied (3 patients). 3/4 had high ER/PR expression (mean DOTA SUV max 9.4) and 1/4 low ER/PR expression (DOTA SUV max 3.1). CONCLUSION: Whilst we have not demonstrated DOTA to be superior to FDG in staging of ER+ /PR+ breast cancers, DOTA may have a role in assessing HR status and treatment decisions; further evaluation of this is warranted.

Rapid Modulation of PSMA Expression by Androgen Deprivation: Serial 68Ga-PSMA-11 PET in Men with Hormone-Sensitive and Castrate-Resistant Prostate Cancer Commencing Androgen Blockade.

Prostate-specific membrane antigen (PSMA) may be targeted for both diagnostic and therapeutic purposes in the management of prostate cancer (PCa). In preclinical models, androgen blockade (AB) increases expression of PSMA in both hormone-sensitive and castrate-resistant xenotypes. The aim of this study was to evaluate the effect of AB treatment on 68Ga-PSMA-11 PET imaging in hormone-naive (luteinizing hormone-releasing hormone [LHRH] ± bicalutamide) and in castrate-resistant men (enzalutamide or abiraterone) with metastatic PCa. Methods: Serial 68Ga-PSMA-11 PET was prospectively performed at baseline and on days 9, 18, and 28 in 8 men with measurable metastatic hormone-sensitive PCa commencing LHRH ± bicalutamide (cohort 1) and 7 men with castrate-resistant PCa commencing either enzalutamide or abiraterone (cohort 2). Gleason score, age, time since diagnosis, and prior treatments were documented. Testosterone and prostate-specific antigen (PSA) were measured at baseline and all imaging time points. PET/CT was quantitatively analyzed for SUVmax, SUVmean, and total tumor volume. Results: In cohort 1, a median 30% (interquartile range [IQR], 5-61) reduction in SUVmax was recorded by day 9 after AB. A reduction from baseline SUVmax occurred in 86.5% (6/7) men by day 9 (P < 0.04), with an associated PSA response in 100% men (P < 0.03). Total tumor volume reduced in all men by 74.5% (IQR, 27-97) (P < 0.02). After day 9, PSMA response heterogeneity was noted, with persistently high or increasing SUVmax in 37.5% (3/8) and marked reduction in 62.5% (5/8). In cohort 2, a median 45% (IQR, 12.7-66) increase in intensity of PSMA SUV was recorded by day 9 after AB. All men demonstrated an increase in SUVmax and SUVmean on PSMA PET compared with baseline (P < 0.04). This increase at day 9 plateaued by day 28. PSA responses were more delayed in cohort 2 (-15% [IQR, 70-138]), with 2 of 7 men demonstrating PSA progression. Conclusion: There is rapid dichotomous response on 68Ga-PSMA PET imaging to AB-dependent on the presence of a hormone-sensitive or castrate-resistant PCa phenotype. This has important implications for interpretation of PSMA PET, and in the timing and sequencing of PSMA-targeted therapy.

68Ga-HBEDD PSMA-11 PET/CT staging prior to radical prostatectomy in prostate cancer patients: Diagnostic and predictive value for the biochemical response to surgery.

METHODS:: We analysed results of 142 males with staging PSMA prior to radical prostatectomy (RP). Data collected included PSMA PET/CT, bone scan (30/142), mpMRI (112/142), and pathological T stage (pT) stage, Gleason score, surgical margins and lymph node status at RP. Prostate-specific antigen (PSA) was documented at staging scan, and following surgery (median 45 days (interquartile range 38-59). A PSA of < 0.03 ng ml-1 was classified as surgical response (SR). Logistic regression was performed for association of pre-operative clinical variables and SR. RESULTS:: 97.9% (139/142) of males had positive intraprostatic findings on PSMA. 14.1 % (20/142) of males had further sites of extra prostatic disease identified on PSMA PET. In males with disease confined to the prostate, 82.9 % (92/111) achieved an SR, compared to 28.6 % (4/14) in males with extraprostatic disease identified (lymph node positive and distant metastatic disease) (p < 0.001). On binary logistic regression PSMA had a superior predictive value for SR than Gleason score, PSA (at time of imaging) or pT stage. MRI was less sensitive and more specific for SVI, and less sensitive for nodal involvement. CONCLUSION:: Extraprostatic disease identified on staging pre-operative PSMA PET is independently predictive of a poor surgical response to RP, and may indicate a need for a multimodality approach to treatment. ADVANCES IN KNOWLEDGE:: This is one of the first studies to correlate the PSMA PET's staging capacity to prostate cancer patient's outcomes to radical prostatectomy and indicates it's potential in predicting which patients will benefit from radical prostatectomy.

Impact of Patient Preparation on the Diagnostic Performance of 18F-FDG PET in Cardiac Sarcoidosis: A Systematic Review and Meta-analysis.

PURPOSE: F-FDG PET/CT is a valuable diagnostic tool in the evaluation of cardiac sarcoidosis. Appropriate patient preparation is important because the diagnostic accuracy of this procedure depends on adequate suppression of physiologic glucose uptake. This systematic review and meta-analysis aims to assess the effect of different patient preparations on the diagnostic accuracy of F-FDG PET/CT in cardiac sarcoidosis. PATIENTS AND METHODS: We searched the PubMed/MEDLINE, Embase, and Cinicaltrials.gov databases. Sixteen studies (n = 559) were identified to be suitable for this systemic review. Studies were stratified according to fasting duration and means of physiologic suppression of F-FDG by cardiac tissue, which involves the use of heparin infusion or high-fat, low-carbohydrate diet before imaging. Study quality was assessed using the QUADAS-2 tool. Forest plots of sensitivity and specificity were calculated in Review Manager 5.3, and a random-effects hierarchical summary receiver operating characteristic model was created using MetaDiSc. Meta-regression was performed to investigate sources of heterogeneity. RESULTS: PET/CT had an overall Specificity of 0.75 (95% confidence interval [CI], 0.69-0.80) and specificity of 0.81 (95% CI, 0.76-0.85) for the diagnosis of cardiac sarcoidosis. This modest diagnostic accuracy was attributed to the inclusion of large single study in which a short fasting duration before scanning likely influenced its sensitivity. Its exclusion resulted in an overall sensitivity of 0.81 (95% CI, 0.76-0.86) and specificity of 0.82 (95% CI, 0.77-0.86). Meta-regression showed that the diagnostic odds ratio was significantly affected by fasting time and heparin administration before scanning (P = 0.01, 0.02) but not with high-fat, low-carbohydrate diet (P = 0.17). CONCLUSIONS: F-FDG PET/CT plays an integral role in the diagnosis of cardiac sarcoidosis. Diagnostic accuracy is affected by fasting duration and means of cardiomyocyte glucose uptake suppression before scanning.

Prospective Comparison of 18F-Fluoromethylcholine Versus 68Ga-PSMA PET/CT in Prostate Cancer Patients Who Have Rising PSA After Curative Treatment and Are Being Considered for Targeted Therapy.

UNLABELLED: In prostate cancer with biochemical failure after therapy, current imaging techniques have a low detection rate at the prostate-specific antigen (PSA) levels at which targeted salvage therapy is effective. (11)C-choline and (18)F-fluoromethylcholine, though widely used, have poor sensitivity at low PSA levels. (68)Ga-PSMA (Glu-NH-CO-NH-Lys-(Ahx)-[(68)Ga-N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid]) has shown promising results in retrospective trials. Our aim was to prospectively compare the detection rates of (68)Ga-PSMA versus (18)F-fluoromethylcholine PET/CT in men who were initially managed with radical prostatectomy, radiation treatment, or both and were being considered for targeted therapy. METHODS: A sample of men with a rising PSA level after treatment, eligible for targeted treatment, was prospectively included. Patients on systemic treatment were excluded. (68)Ga-PSMA, (18)F-fluoromethylcholine PET/CT, and diagnostic CT were performed sequentially on all patients between January and April 2015, and the images were assessed by masked, experienced interpreters. The findings and their impact on management were documented, together with the results of histologic follow-up when feasible. RESULTS: In total, 38 patients were enrolled. Of these, 34 (89%) had undergone radical prostatectomy and 4 (11%) had undergone radiation treatment. Twelve (32%) had undergone salvage radiation treatment after primary radical prostatectomy. The mean PSA level was 1.74 ± 2.54 ng/mL. The scan results were positive in 26 patients (68%) and negative with both tracers in 12 patients (32%). Of the 26 positive scans, 14 (54%) were positive with (68)Ga-PSMA alone, 11 (42%) with both (18)F-fluoromethylcholine and (68)Ga-PSMA, and only 1 (4%) with (18)F-fluoromethylcholine alone. When PSA was below 0.5 ng/mL, the detection rate was 50% for (68)Ga-PSMA versus 12.5% for (18)F-fluoromethylcholine. When PSA was 0.5-2.0 ng/mL, the detection rate was 69% for (68)Ga-PSMA versus 31% for (18)F-fluoromethylcholine, and when PSA was above 2.0, the detection rate was 86% for (68)Ga-PSMA versus 57% for (18)F-fluoromethylcholine. On lesion-based analysis, (68)Ga-PSMA detected more lesions than (18)F-fluoromethylcholine (59 vs. 29, P < 0.001). The tumor-to-background ratio in positive scans was higher for (68)Ga-PSMA than for (18)F-fluoromethylcholine (28.6 for (68)Ga-PSMA vs. 9.4 for (18)F-fluoromethylcholine, P < 0.001). There was a 63% (24/38 patients) management impact, with 54% (13/24 patients) being due to (68)Ga-PSMA imaging alone. Histologic follow-up was available for 9 of 38 patients (24%), and 9 of 9 (68)Ga-PSMA-positive lesions were consistent with prostate cancer ((68)Ga-PSMA was true-positive). The lesion positive on (18)F-fluoromethylcholine imaging and negative on (68)Ga-PSMA imaging was shown at biopsy to be a false-positive (18)F-fluoromethylcholine finding ((68)Ga-PSMA was true-negative). CONCLUSION: In patients with biochemical failure and a low PSA level, (68)Ga-PSMA demonstrated a significantly higher detection rate than (18)F-fluoromethylcholine and a high overall impact on management.

Dual-time-point (18)F-FDG-PET/CT imaging in the assessment of suspected malignancy.

UNLABELLED: INTRODUCTION (PURPOSE OF THE STUDY): The objective of this study was to assess whether dual-time-point (18)F-fluoro-2-deoxyglucose ((18)F-FDG)-PET/CT imaging improved the evaluation of suspected malignancy and if there was any resulting change in management. METHODS: A total of 53 patients with suspected malignancy were investigated by performing two static acquisitions started at mean times t = 64 and t = 155 min after the tracer injection. The total number of malignant lesions was 133 and the total number of benign lesions was 61. Visual and semiquantitative analysis was performed on both the early and delayed images. RESULTS: Overall, there was a significant improvement (P < 0.001) in the sensitivity of delayed imaging (94%) compared with early imaging (77%) in detecting malignant lesions, without a reduction in specificity. In 10 patients, 13 malignant lesions were undetected on early imaging alone but detected on delayed imaging. In seven patients, 10 malignant lesions were incorrectly classified as 'likely benign' on early imaging but correctly reported as 'likely malignant' on delayed imaging. Management was altered in 2 out of 17 patients. Overall, delayed imaging altered management in 2 out of 53 studied patients. Dual-time-point (18)FDG-PET/CT imaging was useful in differentiating malignant from benign intra-abdominal lesions but did not improve the evaluation of pulmonary lesions. CONCLUSIONS: (18)F-FDG-PET/CT imaging should be performed as late as reasonably possible after tracer administration in order to increase tumour-to-background contrast and thereby improve the sensitivity of demonstrating additional sites of disease. Dual-time-point (18)FDG-PET/CT may be of benefit in the evaluation of intra-abdominal lesions but does not improve the overall evaluation of pulmonary lesions.