Does finasteride (1 mg) increase the risk of prostate cancer?

Finasteride 1 mg Does Not Increase the Risk of Prostate Cancer

Finasteride 1 mg used for treating androgenic alopecia does not increase the risk of prostate cancer, and may actually reduce the overall risk of prostate cancer development. 1 The initial concerns about high-grade prostate cancer risk have been largely attributed to detection bias rather than a true biological effect.

Understanding the Evidence on Finasteride and Prostate Cancer Risk

Initial Concerns and Subsequent Clarification

The Prostate Cancer Prevention Trial (PCPT) initially raised concerns when it showed that while finasteride 5 mg reduced overall prostate cancer incidence by 24.8%, there appeared to be an increase in high-grade prostate cancers 2. However, subsequent analyses have provided important context:

• Multiple analyses suggest the apparent increase in high-grade cancers was due to detection bias rather than a true biological effect 1
• Several factors contributed to this detection bias:
  • Finasteride reduces prostate volume by 25-30%, making cancer detection more likely during biopsy 1
  • The smaller prostate size with finasteride use increases the likelihood of detecting all grades of cancer 1
  • Enhanced sensitivity of PSA and digital rectal examination in the finasteride group 1

Bias-Adjusted Analyses

When accounting for these biases:

• Modeling incorporating prostate volume suggests the increase in high-grade cancers was nearly completely explained by enhanced detection 1
• A bias-adjusted analysis showed a 27% lower rate of high-grade cancer in the finasteride arm (6.0%) compared to placebo (8.2%) 3
• Detailed analysis of biopsy specimens showed men taking finasteride had smaller, less aggressive tumors compared to placebo 1

Finasteride 1 mg vs. 5 mg Dosing

The evidence specifically regarding the 1 mg dose used for alopecia:

• The PCPT study used 5 mg finasteride, while the dose for androgenic alopecia is 1 mg 4
• The 1 mg dose has a better side effect profile than the 5 mg dose 4
• The 1 mg dose has similar effects on PSA levels as the 5 mg dose in men over 50 4, 5
• The 1 mg dose causes a median decrease in serum PSA of 40% in men aged 40-49 and 50% in men aged 50-60 5

Clinical Implications and Monitoring

For men taking finasteride 1 mg for alopecia:

• Regular PSA monitoring should be considered for men over 50 4
• When interpreting PSA results, a multiplier (approximately 2x) should be applied to account for finasteride's effect on PSA levels 4, 5
• The PSA-lowering effect of finasteride 1 mg is similar to that of the 5 mg dose, suggesting the same PSA adjustment recommendations should apply 5

Important Considerations and Caveats

• The primary side effects of finasteride are sexual in nature, including decreased libido, erectile dysfunction, and reduced ejaculate volume 4, 6
• Gynecomastia occurs in approximately 2.2% of patients on long-term finasteride treatment 4
• The FDA has added warnings about potential persistent sexual side effects to the drug label 4
• These side effects should be discussed and weighed against the benefits of treatment for androgenic alopecia

Conclusion

Based on the most recent and highest quality evidence, finasteride 1 mg used for androgenic alopecia does not increase the risk of prostate cancer. In fact, it may provide some protective effect against overall prostate cancer development. The initial concerns about high-grade prostate cancer have been largely attributed to detection bias rather than a true biological effect.