German multicenter study investigating ¹⁷⁷Lu-PSMA-617 radioligand therapy in advanced prostate cancer patients

Abstract

¹⁷⁷Lutetium labeled PSMA-617 is a promising new therapeutic agent for radioligand therapy (RLT) of patients with metastatic castration resistant prostate cancer (mCRPC). Initiated by the German Society of Nuclear Medicine a retrospective multicenter data analysis was started in 2015 to evaluate efficacy and safety of ¹⁷⁷Lu-PSMA-617 in a large cohort of patients. Methods: 145 patients (median age 73 years, range 43-88) with mCRPC were treated with ¹⁷⁷Lu-PSMA-617 in 12 therapy centres between February 2014 and July 2015 with one to four therapy cycles and an activity range of 2 to 8 GBq per cycle. Toxicity was categorized by the common toxicity criteria for adverse events (CTCAE 4.0) based on serial blood tests and the attending physician’s report. Primary endpoint for efficacy was biochemical response as defined by a PSA decline ≥ 50% from baseline to at least two weeks after start of RLT. Results: A total of 248 therapy cycles were performed in 145 patients. Data for biochemical response were available in 99 patients and data for physician-reported/lab-based toxicity in 145/121 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, while 40% of patients already responded after a single cycle. Elevated alkaline phosphatase and presence of visceral metastases were negative predictors and the total number of therapy cycles positive predictors of biochemical response. Conclusion: The present retrospective multicenter study of ¹⁷⁷Lu-PSMA-617 RLT demonstrates favorable safety and high efficacy exceeding those of other third line systemic therapies in mCRPC patients. Future Phase II/III studies are warranted to elucidate the survival benefit of this new therapy in patients with mCRPC.