Effect of α1-Adrenoceptor Antagonist Exposure on Prostate Cancer Incidence: An Observational Cohort Study

Purpose: The quinazoline based α1-adrenoceptor antagonists doxazosin and terazosin suppress prostate tumor growth via the induction of apoptosis and decrease in tissue vascularity. To assess the effect of α1-blocker exposure on the incidence of prostate cancer we performed an exploratory, observational cohort study. Materials and Methods: The medical records of all male patients enrolled at Lexington Veterans Affairs Medical Center were searched to identify men treated with quinazoline based α1-adrenoreceptor antagonists between January 1, 1998 and December 31, 2002 for hypertension and/or benign prostatic enlargement. Medical records were subsequently linked to the Markey Cancer Center Kentucky Cancer Registry, a statewide population based central cancer registry that is part of the National Cancer Institute Surveillance, Epidemiology and End Results Program, to identify all incident prostate cancer cases diagnosed. All newly diagnosed prostate cancer cases unexposed to α1-adrenoreceptor antagonists in the total male Veterans Affairs population during this period were also identified from the Kentucky Cancer Registry database. Measures of disease incidence, relative risk and attributable risk were calculated to compare the risk of prostate cancer in α1-blocker exposed vs unexposed men. Kaplan-Meier curves and Cox regression models were used to compare overall survival between α1-blocker exposed and unexposed prostate cancer cases. Results: Our analysis revealed a cumulative incidence of 1.65% in α1-blocker exposed men compared to 2.41% in the unexposed group. These data yielded an unadjusted RR of 0.683 (95% CI 0.532, 0.876) and a risk difference of -0.0076, indicating that 7.6 fewer prostate cancer cases developed per 1,000 exposed men. Thus, exposure to quinazoline α1-blockers may have prevented 32 prostate cancer cases among the 4,070 treated men during the study period. Therefore, men exposed to quinazoline α1-adrenoceptor antagonists were at 1.46 times lower RR and 31.7% lower attributable risk for prostate cancer than unexposed men. There was no association between α1-adrenoceptor antagonist exposure and overall survival. Conclusions: These data suggest that exposure to quinazoline based α1-adrenoceptor antagonists significantly decreases the incidence of prostate cancer. This evidence suggests that the apoptotic and anti-angiogenic effects of these drugs may prevent the development of prostate cancer.