Venous thromboembolism and cyproterone acetate in men with prostate cancer: a study using the General Practice Research Database

OBJECTIVE To evaluate the risk of venous thromboembolism (VTE) associated with the use of cyproterone acetate (CPA) amongst men with prostate cancer. PATENTS AND METHODS Using data from the General Practice Research Database, cases of VTE were identified amongst men with prostate cancer. Four controls with no evidence of a VTE were selected for each case. The time from diagnosis of prostate cancer to first hormonal treatment, and from first hormonal treatment to VTE, was compared for different treatments. Adjusted risk estimates for VTE were derived from further analysis using a nested case-control study design amongst all men with advanced prostate cancer, qualified by evidence of hormonal treatment. RESULTS The time between diagnosis and first treatment was significantly shorter for men first treated with CPA than for men first treated with a luteinizing hormone releasing hormone (LHRH) analogue (adjusted hazard ratio 1.33, 95% confidence interval, CI, 1.06-1.67). When the first treatment was CPA, the treatment-free period after diagnosis was significantly shorter for men who later had a VTE than for those who did not. The case-control study yielded an adjusted risk estimate for VTE amongst CPA users that was significantly higher than amongst men who were prescribed an LHRH analogue or who had had an orchidectomy (adjusted odds ratio 5.23, 95% CI 3.12-8.79). CONCLUSION There was a greater risk of VTE associated with CPA, which might be due to differences in disease severity between users of different products. The clinical significance of this finding is unclear.