The effect of warfarin use on clinical stage and histological grade of prostate cancer.
Pharmacoepidemiol Drug Saf. 2010 May;19(5):436-9. PMID: 20437456
Centre for Clinical Epidemiology and Community Studies, Jewish General Hospital, McGill University, 3755 Côte Ste-Catherine Road, Suite A-114, Montreal, Quebec, H3T 1E2, Canada. Vicky.Tagalakis@mcgill.ca
PURPOSE: Prolonged warfarin use may decrease the risk of prostate cancer. We aimed to assess the effect of warfarin on histological grade and clinical stage of prostate cancer at diagnosis. METHODS: We carried out a retrospective population-based cohort study of men older than 50 years of age diagnosed with prostate cancer between 1985 and 2002 and registered with the Saskatchewan Cancer Registry. We compared a composite score of histological grade and clinical stage of prostate cancer at diagnosis according to warfarin use in the 5 years preceding the diagnosis of prostate cancer. RESULTS: Compared with non-users, men with at least 2 years of cumulative warfarin use in the 5 year period preceding the diagnosis of prostate cancer were at a lower risk of a poor prognosis composite score at the time of their prostate cancer diagnosis (OR 0.40, 95%CI (0.19-0.83)), and when intermediate and poor prognosis scores were combined, a similar estimate of association was observed (OR 0.55, 95%CI (0.33-0.91)), adjusted for age at diagnosis and year of diagnosis. However, an increased risk of poor prognosis disease was observed with 4 years of cumulative warfarin use compared to never use (OR 2.2, 95%CI (1.03-4.81)). CONCLUSIONS: There is a suggestion that at least 2 years of warfarin use is associated with a more favourable prognosis but that extended duration of use beyond 2 years may be associated with poor prognosis disease. Further investigation with a more complete assessment of confounders and that addresses potential detection biases is warranted.