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

To evaluate feasibility, additional benefit and toxicity of treatment extension of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) in patients with metastatic castration-resistant prostate cancer (mCRPC). Methods: From 208 patients treated with 177 Lu-PSMA every 6-8 weeks, 26 patients who had not progressed and not experienced ≥grade 3 toxicity after 6 cycles continued to receive 177 Lu-PSMA until disease progression or complete remission or removal from treatment for toxicity or patient preference. Response rates, the additional benefit of treatment extension, and toxicity were assessed. Results: During treatment extension (up to 13 cycles), 50% of patients achieved an additional PSA decline (-52%±34%, range 1% to 100%), with 8% of patients receiving congruent PSA-based and imaging-based complete response. Median PFS was 450 days. Acute toxicity, including myelosuppression, was mild (≤ grade 2). Xerostomia and chronic kidney disease became more common with repetitive dosing. Conclusion: Extension of 177 Lu-PSMA treatment is feasible and effective in mCRPC.