Mortality in Castration Resistant Prostate Cancer Patients With and Without Pre‐Existing Cardiovascular Disease Receiving Oral Androgen Receptor Pathway Inhibitors

ABSTRACT Background Men with castration‐resistant prostate cancer (CRPC) who have a pre‐existing history of cardiovascular disease (CVD) or other comorbidities are often excluded from clinical trials involving oral androgen receptor pathway inhibitors (ARPi). In this study, we compared all‐cause and prostate cancer‐specific mortality among CRPC patients, with and without a pre‐existing history of CVD, receiving ARPi compared to chemotherapy. Methods Men with CRPC were identified using the Surveillance, Epidemiology, and End Results‐Medicare Linked Database from 2004 to 2015. Patients were grouped into two analytical cohorts by drug use. Inverse probability treatment weights (IPTW)‐adjusted Cox models and Fine‐Gray subdistribution hazards models were used to evaluate associations between ARPi and chemotherapy, and between ENZ and AA for all‐cause mortality and cancer‐specific mortality separately. Results The study cohort included 1438 men with CRPC. Nearly 54.4% of patients had a pre‐existing history of CVD. Patients with a pre‐existing history of CVD had a higher incidence of all‐cause and prostate cancer‐specific mortality compared to patients without a history of CVD (all‐cause mortality: 69.7% vs. 59.3%, prostate cancer‐specific mortality: 56.0% vs. 49.5%, respectively). In the pre‐existing history of CVD cohort, the IPTW‐adjusted Cox model showed a significantly lower all‐cause mortality in patients who received APRi, enzalutamide, and abiraterone, versus chemotherapy (IPTW‐adjusted hazard ratio AHR, 0.56; 95% Confidence Interval CI, 0.48–0.64; p ‐value < 0.001). Further, the IPTW‐adjusted competing risk model showed significantly lower prostate cancer‐specific mortality in patients who received ARPi compared with those who received chemotherapy (IPTW‐AHR, 0.48; 95% CI, 0.41 to 0.57; p ‐value < 0.001). In the without pre‐existing history of CVD cohort, the adjusted Cox model showed significantly lower all‐cause mortality in patients who received APRi than those who received chemotherapy (IPTW‐AHR, 0.49; 95% CI, 0.41–0.60; p ‐value < 0.001). Whereas the IPTW‐adjusted competing risk model showed significantly lower prostate cancer‐specific mortality in patients who received ARPi compared with those who received chemotherapy (IPTW‐AHR, 0.52; 95% CI, 0.42–0.64; p ‐value < 0.001). Conclusion In this population‐based cohort of older men with castration‐resistant prostate cancer, treatment with oral androgen receptor pathway inhibitors was associated with lower estimated risks of all‐cause and prostate cancer–specific mortality compared with chemotherapy in patients with and without pre‐existing CVD. These findings add real‐world comparative effectiveness evidence for patient populations not well represented in randomized clinical trials; however, given the observational design and limitations of administrative data, residual confounding and unmeasured clinical differences may have influenced the results.