Risk of thromboembolic disease in men with prostate cancer undergoing androgen deprivation therapy

Objectives To investigate the risk of thromboembolic disease (TED) in men with prostate cancer (PCa) on androgen deprivation therapy (ADT), while accounting for known TED risk factors. Materials and Methods We assessed TED risk for 42 263 men with PCa who were receiving ADT compared with a matched cohort of 190 930 without PCa. The associations between ADT and deep vein thrombosis (DVT) or pulmonary embolism (PE) were analysed using multivariate Cox proportional hazard regression models, while accounting for previous PCa-related surgeries and the following proxies for disease progression: transurethral resection of the prostate, palliative radiotherapy and nephrostomy. Results Between 1997 and 2013, 11 242 men with PCa received antiandrogen monotherapy, 26 959 men received gonadotropin-releasing hormone (GnRH) agonists, 1 091 men received combined androgen blockade and 3 789 men underwent orchiectomy. When accounting for previous surgeries and proxies of disease progression, GnRH agonist users and surgically castrated men had a higher risk of TED than the comparison cohort: hazard ratios (HRs) 1.67 (95% confidence interval [CI] 1.40-1.98) and 1.61 (95% CI 1.15-2.28), respectively. Men on anti-androgen monotherapy had a lower risk: HR for DVT 0.49 (95% CI 0.33-0.74). TED risk was highest among those who switched from anti-androgen to GnRH agonists: HR for PE 2.55 (95% CI 1.76-3.70). This increased from 2.52 (95% CI 1.54-4.12) in year 1, to 4.05 (95% CI 2.51-6.55) in year 2. Conclusion The incidence of TED among men on ADT increased with the duration of therapy and the risk was highest for those who switched regimen, suggesting that disease progression as well as ADT contribute to the propagation of TED risk. Nonetheless, these findings support the hypothesis that only men with a relevant indication should receive systemic ADT.