177Lu-PSMA for Extended Treatment of Metastatic Castration-Resistant Prostate Cancer

Our objective was to evaluate the feasibility, additional benefit, and toxicity of extending prostate-specific membrane antigen (PSMA)targeted radioligand therapy in patients with metastatic castration-resistant prostate cancer. Methods: From 208 patients treated with Lu-177-PSMA every 6-8 wk, 26 who had not progressed and not experienced grade 3 or higher toxicity after 6 cycles continued to receive Lu-177-PSMA until disease progression, complete remission, or removal from treatment because of toxicity or patient preference. Response rates, the additional benefit of treatment extension, and toxicity were assessed. Results: During treatment extension (<= 13 cycles), 50% of patients achieved an additional prostate-specific antigen decline (-52% +/- 34%; range, -1% to -100%), with 8% of patients achieving a congruent prostate-specific antigen-based and imaging-based complete response. Median progression-free survival was 450 d. Acute toxicity, including myelosuppression, was mild (<= grade 2). Xerostomia and chronic kidney disease became more common with repetitive dosing. Conclusion: Extension of Lu-177-PSMA treatment is feasible and effective inmetastatic castration-resistant prostate cancer.