Diagnostic Impact of Dual-Time PET/CT with (68)Gallium-PSMA in Prostate Cancer and (68)Gallium-DOTATOC in Neuroendocrine Tumors

Background: The timing of imaging for (68)gallium ((68)Ga)-PSMA and (68)Ga-DOTATOC are stated to be around 60 min post-injection (p.i.). In some lesions, late imaging (3–4 h p.i.) showed advantages. The aim of our evaluation was to demonstrate the relevance of an “early” late acquisition. Methods: We retrospectively evaluated 112 patients who underwent (68)Ga-DOTATOC-PET/CT and 82 patients who underwent (68)Ga-PSMA-PET/CT. The first scan was acquired 60 min (±15 min) after application. In cases of diagnostic ambiguity, a second scan was performed 30–60 min later. Pathological lesions were analyzed. Results: Almost half of all (68)Ga-DOTATOC cases and about one-third of all (68)Ga-PSMA examinations showed a change in findings due to the second acquisition. In total, 45.5% of neuroendocrine tumor (NET) patients and 66.7% of prostate cancer (PCa) patients showed relevant TNM classification changes. For (68)Ga-PSMA, there were significant increases in sensitivity and specificity from 81.8% to 95.7% and from 66.7% to 100%, respectively. Statistically significant improvements in sensitivity (from 53.3% to 93.3%) and specificity (from 54.6% to 86.4%) were demonstrated for NET patients. Conclusion: Early second images can improve diagnostics with (68)Ga-DOTATOC and (68)Ga-PSMA PET/CT.