Risk of colorectal adenocarcinoma in men receiving androgen deprivation therapy for prostate cancer; a nationwide cohort study.

ABSTRACT

PURPOSE: To assess whether androgens play a role in explaining the sex related differences in the incidence of colorectal cancer (CRC). METHODS: A nationwide matched cohort study was conducted employing the Prostate Cancer data Base Sweden (PCBaSe) 4.0 during the study period 2006-2016. Prostate cancer (PC) patients receiving androgen deprivation therapy (ADT) were treated as exposed. Prostate cancer-free men from the general population were randomly selected and matched to the index case by birth year and county of residence, forming the unexposed group. All were followed until a diagnosis of CRC, death, emigration, or end of the study period. The risk of CRC among ADT exposed PC patients compared to unexposed cancer-free men was calculated using a flexible parametric survival model and expressed as hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: There was an increased risk of CRC among ADT exposed PC patients compared to unexposed cancer-free men (HR 1.27 [95% CI 1.15-1.41]), in particular an increased risk of adenocarcinoma of the colon (HR 1.33 [95% CI 1.17-1.51]) and more specifically an increased risk of adenocarcinoma of the distal colon (HR 1.53 [95% CI 1.26-1.85]). Examination of latency effects yielded significantly decreased HRs over time for CRC (p = 0.049 for trend). CONCLUSIONS: This population-based study found an increased risk of CRC among PC patients exposed to ADT, specifically adenocarcinoma of the distal colon, which indicates an increased association between ADT (PC + ADT) and CRC but not a positive dose-response trend questioning a true causal effect.