Does long-term finasteride therapy affect the histologic features of benign prostatic tissue and prostate cancer on needle biopsy? PLESS Study Group. Proscar Long-Term Efficacy and Safety Study.

OBJECTIVES: Finasteride, a common agent used to treat benign prostatic hyperplasia (BPH), inhibits 5-alpha-reductase. Testosterone is converted by 5-alpha-reductase to the more potent dihydrotestosterone, which is the primary androgen in the prostate. Leuprolide is a stronger antiandrogen that is used to downstage prostate cancer before radical prostatectomy. Leuprolide induces marked atrophy of prostate carcinoma cells, which sometimes makes pathologic diagnosis of cancer difficult, although evaluation at radical prostatectomy is easier than at biopsy. It is unknown whether finasteride produces similar changes, which would result in greater diagnostic difficulty because such changes would be seen on biopsy to rule out cancer in men with suspicious clinical findings treated for BPH. The current study investigated the histologic effects of finasteride therapy on human prostate cancer and benign prostatic tissue on needle biopsy.
METHODS: In blinded manner, we reviewed 53 needle biopsy specimens showing prostate carcinoma (35 treated with finasteride, 18 with placebo). Also reviewed in blinded manner were 50 benign needle biopsy specimens (25 treated with finasteride, 25 with placebo). The Gleason score, number of cores involved, percentage cancer involvement in a core, percentage of atrophic changes in cancer cells, presence of mitoses, blue-tinged mucinous secretions, prominent nucleoli, and high-grade prostatic intraepithelial neoplasia were documented for each case in the cancer group. The percentage of atrophy, basal cell hyperplasia, transitional metaplasia, chronic inflammation, and stromal proliferation was documented for each case in the benign group.
RESULTS: No significant histologic differences were present in either the benign or cancer group between cases treated with finasteride and placebo.
CONCLUSIONS: We conclude that finasteride treatment for BPH does not cause difficulty in the diagnosis of cancer in prostate needle specimens. It is possible that there are severely atrophic areas resulting from finasteride treatment that are undersampled. However, the conclusion that cancer seen on needle biopsy in men treated with finasteride is unaltered and readily identified as cancer remains valid.