(68)Ga-PSMA PET/CT for restaging recurrent prostate cancer: which factors are associated with PET/CT detection rate?

PURPOSE: To assess the association between PSA levels, PSA kinetics and other factors and a pathological (68)Ga-PSMA PET/CT scan in patients with recurrent prostate cancer (rPCa) with biochemical relapse (BR) after radical therapy. METHODS: Seventy consecutive rPCA patients referred for (68)Ga-PSMA PET/CT, matching all the following criteria, were retrospectively evaluated: (a) previous radical prostatectomy or primary radiotherapy with curative intent; (b) BR or persisting high PSA levels after primary treatment; and (c) complete clinical and imaging information. The mean ± SD PSA level was 3.5 ± 5.3 ng/mL (median 1.7, range 0.2 - 32.2 ng/mL), the mean ± SD PSA doubling time (PSAdt) was 6.5 ± 5.5 months (median 5.5, range 1.3 - 31.6 months), and the mean ± SD PSA velocity was 7.9 ± 20.5 (median 2.1, range 0.2 - 147.5 ng/mL/year). Statistical analysis was performed to assess which factors were associated with the detection of rPCa on (68)Ga-PSMA PET/CT. RESULTS: (68)Ga-PSMA PET/CT was positive in 52 of 70 patients (74.2%). In 30 patients (42.8%) lesions limited to the pelvis were detected. Distant lesions were observed in 8 of patients (11.4%). Local plus systemic lesions were detected in 14 patients (20%). PSA level (p = 0.017) and PSAdt (p = 0.0001) were significantly different between PET-positive patients (higher PSA level, shorter PSAdt) and PET-negative patients (lower PSA, longer PSAdt). ROC analysis showed that PSAdt 6.5 months and PSA 0.83 ng/mL were optimal cut-off values. In multivariate analysis PSAdt was associated with (68)Ga-PSMA PET/CT positivity. (68)Ga-PSMA PET/CT was positive in 17 of 20 patients (85%) with PSA <2 ng/mL and PSAdt <6.5 months, and in 3 of 16 patients (18.7%) with PSA <2 ng/mL and PSAdt ≥6.5 months. CONCLUSION: The great potential of (68)Ga-PSMA PET/CT in patients with rPCa and BR was confirmed. PSA and PSAdt were valuable predictors of pathological (68)Ga-PSMA PET/CT findings.

Reduced myocardial 18F-FDG uptake after calcium channel blocker administration. Initial observation for a potential new method to improve plaque detection.

PURPOSE: Physiological glucose uptake by the myocardium may hamper visualization of coronary atherosclerotic plaques in (18)F-FDG PET studies. Intracellular myocardial calcium relates to glucose influx. We assessed whether administration of a calcium channel blocker such as verapamil could decrease myocardial (18)F-FDG uptake in mice. METHODS: Experiments were conducted on ten male C57BL/6JOlaHsd mice. The mice were studied by (18)F-FDG PET/CT under basal conditions and after a single administration of verapamil injected 1 h prior to (18)F-FDG administration at doses of 1 mg/kg (group A, n = 5) and 20 mg/kg (group B, n = 5). PET scanning was started 60 min after injection of (18)F-FDG employing a dedicated small-animal PET/CT system (ARGUS-CT). In each mouse, post-verapamil PET images were coregistered with the basal PET images. Volumetric regions of interest (VOI) were drawn on the basal study containing the myocardium of the whole left ventricle and quantitatively compared with the same VOI applied to the post-verapamil scan. The SUV(mean) was used to express the mean myocardial (18)F-FDG uptake. The relative coefficient of variation (RV) between the basal and post-verapamil conditions was calculated. RESULTS: Verapamil administration decreased myocardial (18)F-FDG uptake in all animals. The median (range) SUV(mean) values in group A were 2.6 (1.6-4.1) under basal conditions and 1.7 (1.1-2.9) after verapamil administration (p = 0.043), and in group B were 1.6 (1.3-2.0) under basal conditions and 1.0 (0.9-1.4) after verapamil administration (p = 0.043). The median (range) RV values were -31% (-5%, -50%) in group A, and -37% (-10%, -51%) in group B (p = 0.6). CONCLUSION: In this animal model there was a significant reduction in (18)F-FDG uptake in the myocardium following verapamil administration. This type of intervention could facilitate the definition of coronary atherosclerotic plaque inflammation on (18)F-FDG PET scans.

Detection of Sarcomatoid Lung Metastasis With 68GA-PSMA PET/CT in a Patient With Prostate Cancer.

A 70-year-old man with prostate cancer (adenocarcinoma; pT3aN0Mx; GS: 4 + 4) underwent radical prostatectomy and lymph node dissection in February 2008. In December 2009, biochemical recurrence occurred and prostate-specific antigen progressively increased to 4.63 ng/mL despite local salvage radiotherapy and androgen deprivation. Ga-PSMA PET/CT showed a positive left iliac lymph node and a pathological left pulmonary lesion, which was highly positive in a subsequent F-FDG PET/CT. Lymph node resection confirmed an adenocarcinoma metastasis of the prostate cancer and lung surgery demonstrated a sarcomatoid metastasis of prostate cancer. After surgery, prostate-specific antigen decreased to 0.03 ng/mL.

Accuracy of [18F]FDG PET/MRI for the Detection of Liver Metastases.

BACKGROUND: The aim of this study was to compare the diagnostic accuracy of [18F]FDG-PET/MRI with PET/CT for the detection of liver metastases. METHODS: 32 patients with solid malignancies underwent [18F]FDG-PET/CT and subsequent PET/MRI of the liver. Two readers assessed both datasets regarding lesion characterization (benign, indeterminate, malignant), conspicuity and diagnostic confidence. An imaging follow-up (mean interval: 185±92 days) and/-or histopathological specimen served as standards of reference. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for both modalities. Accuracy was determined by calculating the area under the receiver operating characteristic (ROC) curve. Values of conspicuity and diagnostic confidence were compared using Wilcoxon-signed-rank test. RESULTS: The standard of reference revealed 113 liver lesions in 26 patients (malignant: n = 45; benign: n = 68). For PET/MRI a higher accuracy (PET/CT: 82.4%; PET/MRI: 96.1%; p<0.001) as well as sensitivity (67.8% vs. 92.2%, p<0.01) and NPV (82.0% vs. 95.1%, p<0.05) were observed. PET/MRI offered higher lesion conspicuity (PET/CT: 2.0±1.1 [median: 2; range 0-3]; PET/MRI: 2.8±0.5 [median: 3; range 0-3]; p<0.001) and diagnostic confidence (PET/CT: 2.0±0.8 [median: 2; range: 1-3]; PET/MRI 2.6±0.6 [median: 3; range: 1-3]; p<0.001). Furthermore, PET/MRI enabled the detection of additional PET-negative metastases (reader 1: 10; reader 2: 12). CONCLUSIONS: PET/MRI offers higher diagnostic accuracy compared to PET/CT for the detection of liver metastases.