Genomic alterations and associated outcomes in patients with PSMA-positive metastatic castration-resistant prostate cancer treated with 177Lu-PSMA-617.

177Lu-PSMA-617 is approved for patients with metastatic castration-resistant prostate cancer (mCRPC). Although treatment is associated with improved outcomes, not all patients benefit and response is heterogeneous. We aim to characterize genomic alterations associated with benefit to 177Lu-PSMA-617. This study used the Prostate Cancer Precision Medicine Multi-Institutional Collaborative Effort (PROMISE) clinical-genomic database (n = 2445). The primary endpoint was ≥50% PSA decline (PSA50) from baseline with 177Lu-PSMA-617 in molecular subgroups. Secondary endpoints included 90% PSA decline (PSA90). Associations were assessed using Fisher's exact test and Cox regression in multivariable analysis. We identified 183 mCRPC patients treated with 177Lu-PSMA-617. Median number of prior lines of mCRPC therapy was 3. Overall, PSA50 was 49%, median progression-free survival was 7.6 months, and median overall survival was 13.9 months. NF1 (n = 8) and FOXA1 alterations (n = 5) were associated with increased PSA50 (88% vs 47%, P = .03 for NF1; 100% vs 47%, P = .03 for FOXA1). Among CRPC sequenced tumors (n = 119), androgen receptor (AR) alterations (n = 58) were associated with lower PSA50 (38% vs 60%, P = .03). While any tumor suppressor genes (TSG) (PTEN, TP53, RB1) (n = 109) or TP53 (n = 83) alteration were associated with lower PSA90 (P = .02 for both), NF1 (n = 8), and FOXA1 alterations were associated with higher PSA90 (P = .03 and P = .003, respectively). This analysis identifies potential genomic predictors of response to 177Lu-PSMA-617, with NF1 and FOXA1 alterations associated with favorable outcomes and AR and TSG alterations with diminished response. These hypothesis-generating findings suggest genomic profiling may inform selection for PSMA-targeted therapy and warrant prospective validation in larger cohorts.