Comparison of early and standard 18F-PSMA-11 PET/CT imaging in treatment-naïve patients with prostate cancer.

Objective: To evaluate the diagnostic performance of dual-time-point ¹⁸F-PSMA-11 PET/CT imaging at 30 and 60 min post-injection (p.i.) in treatment-naïve patients with prostate cancer (PCa).

Methods: Twenty treatment-naïve patients with histology-proven PCa who underwent ¹⁸F-PSMA-11 PET/CT scans at both 30 and 60-min p.i. were retrospectively analyzed. Lesion detection, semi-quantitative analysis of lesion and background, and unspecific bone uptake (UBU) between two time points were evaluated and compared. Besides, interrater reliability was also evaluated.

Results: Lesion detection was consistent at both 30 and 60-min p.i. imaging of 20 patients (mean age 72 ± 9), identifying 27 primary prostate lesions, 84 lymph node metastases, bone metastases in 8 patients, and other metastases in 2 patients. Primary prostate lesions showed no significant difference in SUVmax and target-to-blood pool (T/B) ratios between the two imaging times, while these parameters significantly increased over time in bone metastases. Lymph node metastases showed no significant difference in SUVmax but higher T/B ratios at 60 min compared to 30 min. A higher frequency of UBU was observed at 60 min (37.3%) compared to 30 min (32.3%), with significantly higher SUVmax and T/B ratios at 60 min. 85.6% UBU was categorized as PSMA-RADS 2 at 60 min, and the others were PSMA-RADS 3 or 4. The most frequent localization was vertebrae, followed by ribs. Interrater reliability was almost perfect for lesion detection at both time points.

Conclusion: Early 30-min ¹⁸F-PSMA-11 PET/CT imaging provided comparable PCa lesion detection and semi-quantitative analysis with reduced UBU to the standard 60-min imaging.