Use of 5α-reductase inhibitors for lower urinary tract symptoms and risk of prostate cancer in Swedish men: nationwide, population based case-control study

OBJECTIVE To assess the association between 5α-reductase inhibitor (5-ARI) use in men with lower urinary tract symptoms and prostate cancer risk. DESIGN Nationwide, population based case-control study for men diagnosed with prostate cancer in 2007-09 within the Prostate Cancer data Base Sweden 2.0. SETTING The National Prostate Cancer Register, National Patient Register, census, and Prescribed Drug Register in Sweden, from which we obtained data on 5-ARI use before date of prostate cancer diagnosis. PARTICIPANTS 26,735 cases and 133,671 matched controls; five controls per case were randomly selected from matched men in the background population. 7815 men (1499 cases and 6316 controls) had been exposed to 5-ARI. 412 men had been exposed to 5-ARI before the diagnosis of a cancer with Gleason score 8-10. MAIN OUTCOME MEASURES Risk of prostate cancer calculated as odds ratios and 95% confidence intervals by conditional logistic regression analyses. RESULTS Risk of prostate cancer overall decreased with an increasing duration of exposure; men on 5-ARI treatment for more than three years had an odds ratio of 0.72 (95% confidence interval 0.59 to 0.89; P<0.001 for trend). The same pattern was seen for cancers with Gleason scores 2-6 and score 7 (both P<0.001 for trend). By contrast, the risk of tumours with Gleason scores 8-10 did not decrease with increasing exposure time to 5-ARI (for 0-1 year of exposure, odds ratio 0.96 (95% confidence interval 0.83 to 1.11); for 1-2 years, 1.07 (0.88 to 1.31); for 2-3 years, 0.96 (0.72 to 1.27); for >3 years, 1.23 (0.90 to 1.68); P=0.46 for trend). CONCLUSIONS Men treated with 5-ARI for lower urinary tract symptoms had a decreased risk of cancer with Gleason scores 2-7, and showed no evidence of an increased risk of cancer with Gleason scores 8-10 after up to four years' treatment.