Survival following upfront chemotherapy for treatment-naïve metastatic prostate cancer: a real-world retrospective cohort study

Background: Upfront chemotherapy prolongs overall survival for men with metastatic, hormone-sensitive prostate cancer (mHSPC) based on data from clinical trials. We sought to assess the association between upfront chemotherapy and overall survival in men with mHSPC in a real-world cohort. Methods: We performed a retrospective cohort study of men with de novo, treatment-naïve metastatic prostate cancer from a large, national cancer database in the United States (2014–2015). Men in the upfront chemotherapy group received chemotherapy within 4 months of diagnosis (n = 1033, 28%) versus no chemotherapy or chemotherapy later than 12 months after diagnosis (controls; n = 2704, 72%). Overall survival was assessed using Kaplan–Meier estimates and compared using multivariable Cox regression analysis. Results: After a median follow-up of 23 months, median overall survival was 35.7 months in the upfront chemotherapy group and 32.5 months for controls (log-rank p < 0.001). After adjusting for patient and clinical variables, upfront chemotherapy was associated with longer overall survival (hazard ratio 0.78, 95% confidence interval 0.68–0.89, p < 0.001). In exploratory analyses, the association between upfront chemotherapy and overall survival did not differ by age groups, race, or number of comorbidities (all interaction p > 0.2). Conclusions: In this real-world cohort, upfront chemotherapy for mHSPC was associated with longer overall survival. These data support the continued use of chemotherapy for men with mHSPC regardless of race or age if they are fit for chemotherapy and underscore the importance of evaluating cancer therapeutics outside of clinical trials to demonstrate treatment efficacy in populations that may be underrepresented in clinical trials.