Impact of new systemic therapies on overall survival of patients with metastatic castration-resistant prostate cancer in a hospital-based registry.

ABSTRACT

BACKGROUND: In 2004, docetaxel was shown to prolong the overall survival (OS) of patients with metastatic castration-resistance prostate cancer (mCRPC). Since 2010, five new systemic therapies have been shown to prolong OS in men with mCRPC. We sought to evaluate the aggregate impact of these newer therapies on the OS of patients with mCRPC. METHODS: Two cohorts of patients diagnosed with mCRPC between 2004 and 2007, treated with drugs used in the limited treatment era only (A), and between 2010 and 2013, treated also with newer therapies (B), were identified from the Dana-Farber Cancer Institute database. The analysis endpoint was OS within 5 years after mCRPC diagnosis. Kaplan-Meier method assessed time-to-event distributions with median (95% confidence interval (CI)). A piece-wise regression model assessed the association between endpoint and treatment cohorts with estimate of hazard ratio (HR) with 95% CI within two time segments in univariate and multivariable analyses adjusting for relevant covariates. RESULTS: Compared to cohort A (n = 318), cohort B (n = 272) patients in newer therapy era demonstrated an OS advantage (2.8 vs. 2.2 years) with a 41% decreased risk of death (HR = 0.59; 95% CI, 0.47-0.74; P < 0.0001), and a 3-year OS rate of 46% vs. 33%. This benefit was accentuated (median OS 2.7 vs. 2.1 years; HR = 0.46; 95% CI, 0.32-0.67; P < 0.0001) in patients who initially presented with de-novo metastatic disease (de-novo). On multivariable analysis, longer OS was associated with cohort B vs. A and performance status 0 vs. 1. CONCLUSIONS: Using a single-institution registry, mCRPC patients treated since 2010 had a significant survival improvement vs. those treated before 2010. Although the median survival was only modestly improved and less than predicted when simply adding each newer drug survival advantage, the cumulative benefit from the new therapies was more pronounced in longer-term survivors and de-novo patients.