Allopurinol and the risk of prostate cancer in a Finnish population-based cohort.

Allopurinol reduces oxidative stress and may thus have an anti-inflammatory effect. Previous studies suggest that allopurinol use might decrease the risk of prostate cancer (PCa) among gout patients. We studied the association between allopurinol use and PCa incidence.The cohort consists of 76,874 men without prevalent PCa, originally identified for the Finnish Randomized Study of Screening for Prostate Cancer (FinRSPC). The follow-up started at entry to the trial. We excluded men using allopurinol in the year before entry (wash-out). PCa cases detected during 1996-2015 were identified from the Finnish Cancer Registry. Information on tumor Gleason score and TNM stage were obtained from medical files. Information on PSA level was obtained from screening samples for men in the FinRSPC screening arm and from laboratory databases for men in the control arm. Information on BMI was based on a questionnaire sent to men in the FinRSPC screening arm in 2004-2008. Drug purchase information were obtained from the national prescription database. We used Cox regression (adjusted for age, FinRSPC trial arm, PCa family history and use of other medication) to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of PCa risk by allopurinol use. We analyzed medication as a time-dependent variable to minimize immortal time bias.There were 9062 new PCa diagnoses in the cohort. Follow-up time did not differ by allopurinol use (median 17 yr; IQR 11-19 vs median 17 yr; IQR 12.33-19). The risk of PCa did not differ by allopurinol use (multivariable adjusted HR 1.03; 95% CI 0.92-1.16). Allopurinol use did not associate with the risk of high-grade or metastatic cancer. Cumulative duration or average yearly dose of allopurinol use showed no association with PCa risk. No delayed risk associations were observed in the lag-time analyses.We observed no difference in the PCa risk by allopurinol use.