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5018 Background: 68 Ga prostate specific membrane antigen positron emission tomography/computed tomography ( 6 8 Ga-PSMA PET/CT) is a highly sensitive diagnostic tool whose adoption is constantly increasing in prostate cancer patients, also for monitoring response to therapies. We evaluated the impact of 68 Ga-PSMA PET/CT response, as compared to prostate-specific antigen (PSA) response, in patients treated with enzalutamide as first-line therapy (1L) for mCRPC. Methods: From Oct 2017 to May 2022, in an observational prospective study, 70 consecutive mCRPC patients were treated with 1L enzalutamide 160 mg QD and underwent 68Ga-PSMA PET/CT within 3 weeks before (baseline) and 12 weeks (SD: ±4 weeks) after treatment initiation. We measured at both the timepoints the sum of metabolic total volume (sMTV), mean and maximum standardized uptake volume (sSUVmean and sSUVmax, respectively) and total lesion activity (sTLA), which is the product of MTV and SUVmean, for a maximum of 20 lesions. On the basis of EAU/EANM criteria, patients were categorized as PSMA responders (PET-R, in case of complete/partial response or stable disease) or PSMA non-responders (PET-NR, in case of progressive disease). Based on prostate-specific antigen (PSA), patients were classified as biochemical responders (PSA-R, in case of PSA decrease ≥ 50%) or non-responders (PSA-NR in all other cases). Survival analysis was performed using the Cox regression hazard model and the Kaplan-Meier method. Results: At the data cut-off (31 st Dec 2023), 69 mCRPC patients were considered fully evaluable. The median age was 75 years (range: 47-91), GS was <8 in 24 (35%) and ≥8 in 37 (53%), the median baseline PSA was 2.57 µg/L (range: 0.09-197). We observed a median sSUVmax of 41.6, median SSUVmean of 28.2 and median sTLA of 44.8. The median follow-up was 57 months. In the Table, we reported survival results according to PSA and PET response. Differences between the discordant groups were not statistically significant for both median progression-free survival (mPFS) and median overall survival (mOS) (p=0.09 and 0.41, respectively), even if a positive trend for PET was shown. At multivariate analysis, only sTLA at 12 weeks was significantly associated with both mPFS (p=0.0004) and mOS (p=0.0006). Conclusions: 68Ga-PSMA PET/CT response appeared more accurate than PSA monitoring to predict survival to enzalutamide initiation in mCRPC. Some PET parameters may better predict survival benefit and need future validation. Table: see text
Giunta et al. (Sat,) studied this question.