Real-world practice patterns in veterans with metastatic castration-resistant prostate cancer

Abstract

Background: Metastatic castration-resistant prostate cancer (mCRPC) is incurable, with most patients surviving less than 3 years. However, many treatments that extend survival have been approved in the past decade.

Objective: To describe the patient demographics, disease characteristics, treatment patterns, and outcomes in a cohort of Veterans diagnosed with mCRPC in the Veterans Health Administration.

Design: We identified 3,637 Veterans diagnosed with prostate cancer between January 2006 and August 2015 with evidence of mCRPC through December 2016. We described the most commonly used systemic mCRPC treatments according to mCRPC diagnosis era: Epoch 1 (2006-2010) or Epoch 2 (2011-2016). Patient demographics, disease characteristics, and treatment patterns were examined using descriptive statistics. An unadjusted Kaplan-Meier method was used to estimate the median time to biochemical progression and overall survival (OS) with 95% confidence intervals.

Results: The median age at initial prostate cancer diagnosis was 68 years. Approximately 67% of patients were non-Hispanic white, 29% were black, and 4% were other/unknown. A high-risk Gleason score (8-10) was reported in 748 (67%) of patients in Epoch 1 and 1578 (63%) of patients in Epoch 2, and the median prostate-specific antigen level at initial prostate cancer diagnosis was higher in Epoch 1 patients than in Epoch 2 patients (68 vs. 35 ng/ml). Following mCRPC diagnosis, the most common first-line therapies in Epoch 1 patients were docetaxel (83%) and abiraterone (9%), whereas Epoch 2 patients mainly received abiraterone (47%), docetaxel (36%), and enzalutamide (15%). In Epoch 1 and Epoch 2 patients, the median time to biochemical progression (unadjusted) was 9 and 13 months, respectively, and the median OS (unadjusted) was 15 and 23 months, respectively.

Conclusions: The introduction of new therapies has resulted in increased use of the noncytotoxic agents abiraterone and enzalutamide as first-line treatment in lieu of docetaxel. Our results suggest that more recently diagnosed patients (Epoch 2) have a delayed time to biochemical progression and longer OS (unadjusted) compared with patients diagnosed earlier (Epoch 1).

Keywords: Castration resistant; Metastatic; Practice patterns; Prostate cancer; Real world.