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 ¹⁷⁷Lu-PSMA every 6–8 wk, 26 who had not progressed and not experienced grade 3 or higher toxicity after 6 cycles continued to receive ¹⁷⁷Lu-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 ¹⁷⁷Lu-PSMA treatment is feasible and effective in metastatic castration-resistant prostate cancer.