Quantitative 68 Ga-PSMA-11 PET and Clinical Outcomes in Metastatic Castration-resistant Prostate Cancer Following 177 Lu-PSMA-617 (VISION Trial).

Background Lutetium 177 [ 177 Lu]Lu-PSMA-617 ( 177 Lu-PSMA-617) is a prostate-specific membrane antigen (PSMA)-targeted radioligand therapy for metastatic castration-resistant prostate cancer (mCRPC). Quantitative PSMA PET/CT analysis could provide information on 177 Lu-PSMA-617 treatment benefits. Purpose To explore the association between quantitative baseline gallium 68 [ 68 Ga]Ga-PSMA-11 ( 68 Ga-PSMA-11) PET/CT parameters and treatment response and outcomes in the VISION trial. Materials and Methods This was an exploratory secondary analysis of the VISION trial. Eligible participants were randomized (June 2018 to October 2019) in a 2:1 ratio to 177 Lu-PSMA-617 therapy (7.4 GBq every 6 weeks for up to six cycles) plus standard of care (SOC) or to SOC only. Baseline 68 Ga-PSMA-11 PET parameters, including the mean and maximum standardized uptake value (SUV mean and SUV max ), PSMA-positive tumor volume, and tumor load, were extracted from five anatomic regions and the whole body. Associations of quantitative PET parameters with radiographic progression-free survival (rPFS), overall survival (OS), objective response rate, and prostate-specific antigen response were investigated using univariable and multivariable analyses (with treatment as the only other covariate). Outcomes were assessed in subgroups based on SUV mean quartiles. Results Quantitative PET parameters were well balanced between study arms for the 826 participants included. The median whole-body tumor SUV mean was 7.6 (IQR, 5.8-9.9). Whole-body tumor SUV mean was the best predictor of 177 Lu-PSMA-617 efficacy, with a hazard ratio (HR) range of 0.86-1.43 for all outcomes (all P < .001). A 1-unit whole-body tumor SUV mean increase was associated with a 12% and 10% decrease in risk of an rPFS event and death, respectively. 177 Lu-PSMA-617 plus SOC prolonged rPFS and OS in all SUV mean quartiles versus SOC only, with no identifiable optimum among participants receiving 177 Lu-PSMA-617. Higher baseline PSMA-positive tumor volume and tumor load were associated with worse rPFS (HR range, 1.44-1.53 [ P < .05] and 1.02-1.03 [ P < .001], respectively) and OS (HR range, 1.36-2.12 [ P < .006] and 1.04 [ P < .001], respectively). Conclusion Baseline 68 Ga-PSMA-11 PET/CT whole-body tumor SUV mean was the best predictor of 177 Lu-PSMA-617 efficacy in participants in the VISION trial. Improvements in rPFS and OS with 177 Lu-PSMA-617 plus SOC were greater among participants with higher whole-body tumor SUV mean , with evidence for benefit at all SUV mean levels. ClinicalTrials.gov identifier: NCT03511664 Published under a CC BY 4.0 license. Supplemental material is available for this article.