Real-world clinical outcomes of patients treated with Lu-177-PSMA-617 for metastatic castration-resistant prostate cancer (mCRPC): A single-institution experience.

Abstract

83 Background: The radiopharmaceutical Lu177-PSMA-617 (LuPSMA) was FDA approved in March 2022 for patients with mCRPC previously treated with both an androgen receptor signaling inhibitor (ARSI) and a taxane, if eligible based on PSMA PET. However, data regarding real world LuPSMA treatment outcomes are limited. Methods: This is a retrospective analysis of the first 100 mCRPC patients who received at least 1 cycle of LuPSMA at a single institution from June 2022 to August 2023. Demographic and clinical characteristics as well as laboratory values were collected. Central review of qualifying PSMA PET/CT was performed to assess disease distribution. A PSA decrease of 30%, 50%, or 90% from baseline at any point during treatment was the primary measure of response (PSA30, PSA50, and PSA90 respectively). Results: Of the 100 patients identified, 2 were excluded from analysis due to prior receipt of LuPSMA on clinical trial. Three patients were still receiving LuPSMA at the time of data collection. Median age was 72 (range, 50 - 93) and median number of treatments received was 4.0. On baseline PET/CT, 43 patients (44%) had bone + nodal metastases only, 19 (19%) had bone metastases only, 8 (8%) had nodal metastases only, and 11 (11%) had liver metastases. As for prior therapies, 47% had received ≥2 ARSIs (n=47/98), 48% had received 2 prior taxanes (n= 47/98), 42% had received 1 prior taxane (n=41/98), 17% received radium-223 (n=17/98), and 10% were treated off-label with no prior chemotherapy (n=10/98). Median follow up from the start of LuPSMA treatment was 7.6 months (range= 0.6-14.1 months, n=98). During treatment, 21 (21%) patients achieved a PSA90 response, 51 (52%) patients achieved a PSA50 response and 60 (61%) patients achieved a PSA30 response. An increase or no change in baseline PSA was seen in 28% (n=26/94 evaluable patients). Among patients with an initial rise in PSA after the first treatment, 10% had a subsequent reduction from baseline PSA (n=3/29). Conclusions: In this cohort of heavily pretreated mCRPC patients, we observed a PSA50 response of 54% and 21% of patients experiencing a PSA reduction ≥90%. This data supports the clinical benefit of LuPSMA in real-world clinical practice. Characterization of response rates within subgroups by prior treatment and disease characteristics are ongoing.