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BACKGROUND:
Despite the widespread use of 5-ARIs for benign prostatic hyperplasia (BPH) and chemopreventive indications, there is much controversy regarding the potential risk of high-grade prostate cancer. Our objective was to determine the association between finasteride use, including duration of use, and the development of total, high-grade or lethal prostate cancer.
METHODS:
The Health Professionals Follow-up Study is a prospective cohort of United States male health professionals who were 40 to 75 years old at baseline in 1986. Finasteride use was assessed on questionnaires every two years from 1996, and 38,430 men who were cancer-free in 1996 were followed for prostate cancer diagnosis until 2008. Cox proportional-hazard models were used to estimate risk associated with finasteride use, adjusting for possible confounders including age, time period, recent smoking history, race, family history of prostate cancer, vigorous physical activity, BMI, height, history of diabetes mellitus, history and intensity of PSA testing, history of physical examinations, history of prostate biopsy or rectal ultrasound, statins, digoxin, alpha-blockers, saw palmetto use, and vasectomy.
RESULTS:
During 397,341 person-years of follow-up, we ascertained 3181 prostate cancer cases, 331of which were advanced (regionally invasive, metastatic, or fatal), and 342 of which were high-grade, Gleason grade 8-10. Of the 38,430 men at baseline in 1996, 2301 (6.0%) reported some use of finasteride between 1986 and 2006.The age-adjusted relative risk for ever-use of finasteride compared with never-use was 1.04 (95% confidence interval [CI] = 0.87-1.25) for total disease. After adjusting for confounders including history of PSA screening and prostate biopsy, ever use of finasteride was associated with significantly lower risk of total disease, Gleason 7 and low-grade disease, and localized disease. The multivariable-adjusted relative risk was 0.75 (95% CI = 0.63-0.91) for total disease, 0.61 (95% CI 0.43-0.87) for Gleason 7 disease, and 0.70 (0.53-0.93) for low-grade (Gleason 2-6) disease. Finasteride use was not associated with risk of high-grade (RR=1.04, 95%CI: 0.64-1.69) or advanced disease (RR= 1.03, 95% CI: 0.62-1.73). The relative risk of all types of prostate cancer did not appear to vary by duration of finasteride use of less than four years or four or more years; however, the number of long-term users was low.
CONCLUSIONS:
In this cohort of male health professionals, finasteride use was associated with a decreased risk of overall, low-grade, and Gleason 7 prostate cancer. Finasteride use, however, was not associated with either lowering or increasing the risk of high grade, metastatic or fatal prostate cancer as may have been suggested by previously published studies.