Real-world clinical outcomes and economic burden of early discontinuation of taxane therapy among patients with metastatic castration-resistant prostate cancer.

Abstract

e17043 Background: Despite comprising an important part of the treatment paradigm for metastatic castration-resistant prostate cancer (mCRPC) for over a decade, real-world use of taxanes is hindered by adverse events (AEs). AEs may lead to early treatment discontinuation, which may adversely affect outcomes. The two goals of this study were to determine the proportion of mCRPC patients who discontinue taxanes early (defining the early discontinuation threshold relative to efficacy results associated with androgen receptor pathway inhibitors [ARPIs]) and to evaluate the impact of early discontinuation on clinical outcomes, AEs, and healthcare costs. Methods: This was a retrospective, observational study of adult men with mCRPC treated with an ARPI as their first-line (1L) therapy and who initiated second-line (2L) therapy with another ARPI or a taxane. The Flatiron Health electronic health record database (07/01/2012–06/30/2020) was used to estimate Kaplan-Meier overall survival (OS) curves for the taxane cohort by the number of cycles received; these were compared with patients who received ARPI at 2L. Cox regression modeling and median PFS and OS values were used to identify the number of taxane cycles needed to achieve comparable OS to ARPI. The number of taxane cycles with similar OS outcomes to ARPI was then considered the threshold for early discontinuation. In addition, the IQVIA PharMetrics Plus claims database (01/01/2013–08/31/2021) was used to estimate taxane-related AEs (based on product information) and associated healthcare costs among patients who did and did not discontinue taxanes early. Results: From Flatiron, 473 2L ARPI patients and 214 2L taxane patients were included. Similar clinical characteristics – e.g., prostate-specific antigen level, ECOG performance status, and Gleason score – were observed between the two cohorts. Overall, 2L ARPI was associated with longer median OS (15.4 vs. 13.6 months) than 2L taxane. The number of taxane cycles needed to reach comparable OS to ARPI was determined to be 8. Patients receiving >8 cycles (n=48; 22%) compared to those receiving ≤8 cycles (n=166; 78%) had longer median OS (18.4 vs. 11.9 months, respectively) and PFS (9.0 vs. 4.3 months, respectively). From PharMetrics, 158 2L taxane patients were included. Patients receiving >8 cycles (n=20; 13%) were more likely to experience an AE (95% vs. 88%) than those receiving ≤8 cycles (n=138; 87%) but had lower mean AE-related total healthcare costs per patient per month ($3,429 vs. $6,334). Conclusions: These results suggest that mCRPC patients need to receive >8 cycles of taxane at 2L to receive more clinical benefit than 2L ARPI. However, the vast majority of patients in the study discontinued taxane early, resulting in shorter survival outcomes compared to ARPI.