Finasteride Long-Term Safety: 10-Year Evidence

Bottom line: The available 10-year data from finasteride’s open-label extension study showed that the side effect profile at year 10 was similar to that in earlier years, with no emergence of new safety signals over time. The most concerning long-term question — prostate cancer risk — was addressed by the PCPT trial, which showed a reduced incidence of low-grade prostate cancer but a slightly higher incidence of high-grade tumors (a finding with debated clinical significance).

Key Long-Term Studies

Study	Duration	Key Safety Finding
Propecia 10-year OLE	10 years	Side effect rates stable; 87% maintained/improved hair; no new safety signals
PLESS trial (5 mg BPH)	4 years	Sexual side effects decreased after year 1; favorable cardiovascular and metabolic profile
PCPT trial (5 mg)	7 years	25% reduction in prostate cancer overall; 6.4% vs. 5.1% high-grade (Gleason ≥7) — debated interpretation

Prostate Cancer Risk: The PCPT Controversy

The PCPT finding of more high-grade prostate cancers in the finasteride arm remains debated. Subsequent analysis suggests this is largely a detection bias effect: finasteride shrinks prostate volume, making biopsy sampling more accurate and thus more likely to detect high-grade cancers that were always present. The FDA label includes a cancer risk warning; this should be discussed with your prescribing physician, particularly for men with elevated PSA. See: PCPT trial deep-dive.

See: Cancer risk detailed review | Finasteride and fertility | 10-year study data | PLESS trial review