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.

PurposeTo determine the value of 68Ga-DOTA-TOC and 18F-FDG PET/CT for initial and follow-up evaluation of patients with neuroendocrine tumour (NET) treated with peptide receptor radionuclide therapy (PRRT).MethodsWe evaluated 66 patients who had histologically proven NET and underwent both PRRT and three combined 68Ga-DOTA-TOC and 18F-FDG PET/CT studies. 68Ga-DOTA-TOC PET/CT was performed before PRRT, 3 months after completion of PRRT and after a further 6 – 9 months. 18F-FDG PET/CT was done within 2 months of 68Ga-DOTA-TOC PET/CT. Follow-up ranged from 11.8 to 80.0 months (mean 34.5 months).ResultsAll patients were 68Ga-DOTA-TOC PET-positive initially and at follow-up after the first full PRRT cycle. Overall, 62 of the 198 18F-FDG PET studies (31 %) were true-positive in 38 of the 66 patients (58 %). Of the 66 patients, 28 (5 grade 1, 23 grade 2) were 18F-FDG-negative initially and during follow-up (group 1), 24 (5 grade 1, 13 grade 2, 6 grade 3) were 18F-FDG-positive initially and during follow-up (group 2), 9 patients (2 grade 1, 6 grade 2, 1 grade 3) were 18F-FDG-negative initially but 18F-FDG-positive during follow-up (group 3), and 5 patients (all grade 2) were 18F-FDG-positive initially but 18F-FDG-negative during follow-up (group 4).18F-FDG PET showed more and/or larger metastases than 68Ga-DOTA-TOC PET in five patients of group 2 and four patients of group 3, all with progressive disease. In three patients with progressive disease who died during follow-up tumour SUVmax increased by 41 – 82 % from the first to the last follow-up investigation.ConclusionIn NET patients, the presence of 18F-FDG-positive tumours correlates strongly with a higher risk of progression. Initially, patients with 18F-FDG-negative NET may show 18F-FDG-positive tumours during follow-up. Also patients with grade 1 and grade 2 NET may have 18F-FDG-positive tumours. Therefore, 18F-FDG PET/CT is a complementary tool to 68Ga-DOTA-TOC PET/CT with clinical relevance for molecular investigation.

Peptide receptor radionuclide therapy (PRRT) has been used for more than twenty years as a systemic treatment approach in inoperable or metastatic somatostatin receptor (SSTR)-positive tumors. The purpose of this study was to analyze the long-term outcome of PRRT with regard to the most commonly used radiopharmaceuticals, Y-DOTA-Tyr3-octreotide (Y-DOTA-TOC) and Lu-DOTA-Tyr3-octreotate (Lu-DOTA-TATE). This retrospective clinical study included a total of 44 consecutive patients (27 men) with advanced tumors and enhanced SSTR expression. Mean age at initial diagnosis was 60 years (SD 11.3, range 40 to 84 years). Median follow-up was 80 months. In the mean 5.3 ± 2.5 cycles were administered forLu-PRRT with mean activity of 27.2 ± 14.9 GBq per patient and 5.5 ± 2.6 cycles for Y-PRRT with mean activity of 14.7 ± 7.3 GBq. Overall, 378 cycles were administered (mean 8.6 ± 3.4 cycles per patient) with an overall cumulative activity of 1514.1 GBq. Median overall survival (OS) was 79 months. Twenty-one (77.8%) of the 27 men and nine (52.9%) of the 17 women had died 12 years after commencement of PRRT. Shortest duration of illness was eight months, longest 155 months. Severe side-effects (WHO Grades III and IV) are seen in nine of the 14 patients still alive. Chronic kidney disease in combination with anemia is the most common finding in the nine patients with severe side-effects. Very poor prognosis was found for those patients who showed progressive disease (PD) in comparison with patients with cumulative disease control after initial PRRT (log-rank, p<0.001), while women and patients with no more than two tumor sites seem to especially benefit from PRRT not reaching significance levels. PRRT is very encouraging in terms of long-term outcome. Thirty-two percent (14/44 patients) of the patients with metastatic or inoperable disease are still alive more than 12 years after the beginning of radionuclide therapy. Possible predictors for favourable outcome are initial response to PRRT, number of affected sites and female gender.

Performance of early imaging in Ga-PSMA-11 PET/CT in addition to whole-body scans 60 min p.i. increases the detection rate of local recurrence in PC patients with biochemical recurrence. Acquisition of early PET images should be started as early as 5 min p.i. in order to avoid disturbing tracer activity in the urinary bladder occuring at a later time point.