Safety and efficacy of 177lu-PSMA-617 radioligand therapy in patients with mCRPC: A multicenter study.
155 Background: Prostate specific membrane antigen (PSMA) is a promising target for imaging and therapy of prostate cancer. Small cohorts trials have shown promising results for response and tolerability of 177Lu-PSMA-617 radioligand therapy (RLT) in patients with metastatic castration-resistant disease. The aim of this multicenter study was to investigate safety and efficacy of this new therapy in a large, multicenter cohort. Methods: Data of 145 patients with metastatic castration resistant prostate cancer treated with at least a single dose of 177Lu-PSMA-617 at 12 therapy centers in Germany (median age 73 years, range 43-88) were collected. Up to 4 therapy cycles (range of administered activity 2 – 8 GBq) were given. Toxicity was categorized by the common toxicity criteria for adverse events based on serial blood tests and the physician’s report. Biochemical response was defined by a PSA decline ≥ 50% from baseline. Results: 248 therapy cycles were performed. Data for biochemical response were available in 99 patients and data for physician-reported and lab-based toxicity in 145 and 121 patients. The median follow-up was 16 weeks (range 2-30 weeks). Nineteen patients died during the observation period. Grade 3 to 4 hematotoxicity occurred in 18 patients: 10%, 4% and 3% of the patients experienced anemia, thrombocytopenia and leukopenia, respectively. Xerostomia occurred in 8%. Overall biochemical response rate was 45% following all therapy cycles. Elevated alkaline phosphatase and presence of visceral metastases were negatively correlated and the total number of therapy cycles correlated positively with biochemical response. 22 of 31 patients with no PSA decline > 50% after the first cycle did not respond to the second therapy cycle. Conclusions: Radioligand therapy with 177Lu-PSMA-617 shows promising response rates and a low toxicity in extensively pretreated patients with prostate cancer. Future prospective trials have to evaluate the effect of RLT on survival and potentially be considered in earlier stages of prostate cancer.