Real-world treatment patterns and progression-free survival among patients with metastatic castration-resistant prostate cancer: Examining the benefits of sequential androgen receptor pathway inhibitor use.

Abstract

64 Background: Numerous treatments with different mechanisms of action are approved for metastatic castration-resistant prostate cancer (mCRPC), but real-world studies increasingly indicate that androgen receptor pathway inhibitors (ARPIs) are the most common treatment choice at both first- (1L) and second-line (2L). Nonetheless, robust evidence on the clinical effectiveness of ARPIs when used sequentially is lacking. The aim of this study was to examine the real-world treatment patterns and associated progression-free survival (PFS) among patients with mCRPC in the United States (US). Methods: This retrospective cohort study used Flatiron Health electronic health record data from 01/01/2013 to 06/30/2020. Included patients were male, aged ≥18 years, had a confirmed diagnosis of mCRPC within the study period, and received ≥1 systemic therapy post-mCRPC diagnosis. Three treatment subgroups were examined, with ARPI defined as abiraterone or enzalutamide: all 1L ARPI users; all 2L ARPI users irrespective of 1L therapy; and 1L ARPI users who received another ARPI at 2L. Treatment patterns were evaluated descriptively; time to next therapy (TTNT) was measured from the start of the ARPI of interest to the start of the subsequent line of therapy. The Kaplan-Meier method was used to evaluate PFS from the start of the ARPI therapy of interest until progression or death from any cause. Results: The study included 2,588 patients (mean age 72 years). ARPIs were the most prescribed systemic therapy in both the 1L and 2L settings: 63% (1,634/2,588) and 46% (808/1,760), respectively. Among 1L ARPI patients, 28.9% received 2L ARPI, 14.0% 2L taxane, 14.3% 2L combo therapies, and 32% received no further therapy. The median TTNT was 7.6, 6.2, and 5.1 months for 1L ARPIs, 2L ARPIs among all users, and 2L ARPIs among patients who received 1L ARPIs, respectively. The corresponding median PFS was 6.5 months, 4.5 months, and 3.9 months, respectively. Conclusions: Among real-world mCRPC patients in the US, ARPIs remain the most common therapy at both 1L and 2L. However, sequential ARPI use appeared to provide diminishing returns, with a PFS of <4 months seen at 2L in those who had received 1L ARPIs. [Table: see text]