What are the risks and benefits of continuing Proscar (finasteride) treatment in a patient with a 6-year history of use?

Long-Term Proscar (Finasteride) Use After 6 Years

For patients who have been on Proscar (finasteride) for 6 years, continuation of therapy is reasonable if the medication is providing benefit for benign prostatic hyperplasia (BPH), as the optimal treatment duration based on the landmark PCPT trial was 7 years, though the decision must weigh ongoing benefits against the persistent concern about high-grade prostate cancer risk. 1

Treatment Duration Considerations

The American Society of Clinical Oncology/American Urological Association guideline specifically addresses treatment duration:

• No trial has directly compared different durations of 5α-reductase inhibitors for preventing prostate cancer 1
• The PCPT trial administered finasteride for a planned 7 years, making this the evidence-based benchmark for treatment duration 1
• The panel judged that finasteride should be given for 7 years if used for primary prevention until additional information becomes available 1

At 6 years of treatment, your patient is approaching the studied duration, suggesting continuation for at least one more year is supported by the evidence base.

Ongoing Benefits at 6+ Years

Prostate Cancer Risk Reduction

• Finasteride reduces the period prevalence of for-cause prostate cancer by approximately 26% (relative risk 0.74; 95% CI, 0.67 to 0.83) 1
• The absolute risk reduction is approximately 1.4% (4.9% in controls vs 3.5% in finasteride arms) 1
• In the PCPT, finasteride reduced for-cause prostate cancers with a relative risk of 0.76 (95% CI, 0.68 to 0.86) 1

BPH Symptom Control and Disease Progression

• Long-term finasteride treatment (>2 years) produces sustained prostate volume reduction of approximately 20-28% 2, 3
• Maximum urinary flow rates improve by approximately 3 ml/s with continued therapy 4, 2
• Finasteride reduces the risk of acute urinary retention by 67% compared to placebo 1, 5
• The risk of BPH-related surgery is reduced by 64% with finasteride treatment 1, 5

Critical Safety Concerns at 6 Years

High-Grade Prostate Cancer Risk

The most significant concern with long-term finasteride use is the increased incidence of high-grade (Gleason 8-10) prostate cancer observed in the PCPT trial 1:

• Gleason 8-10 prostate cancer occurred in 1.8% of finasteride-treated men versus 1.1% in placebo 5
• For every 1,000 men treated, finasteride reduces total prostate cancers from 60 to 45, but increases high-grade cancers from 18 to 21 1

Important context: Subsequent analyses suggest this increase may be artifactual rather than causal 1:

• Detailed pathologic review eliminated morphologic artifact as an explanation 1
• Finasteride reduces prostate volume by 25%, which decreases sampling error during biopsy and may enhance detection of high-grade cancers rather than causing them 1
• Modeling incorporating prostate volume suggests the increase may be nearly completely explained by enhanced detection 1

Mortality Data

• No difference in prostate cancer-specific mortality (relative risk 1.00; 95% CI, 0.29 to 3.47) 1
• No difference in all-cause mortality (relative risk 1.06; 95% CI, 0.95 to 1.18) 1

Persistent Adverse Effects

Sexual Side Effects (Long-term data >2 years)

• Erectile dysfunction/impotence: 67.4% with finasteride vs 61.5% with placebo (RR 1.10; 95% CI, 1.07 to 1.12) 1
• Decreased ejaculate volume: 60.4% with finasteride vs 47.3% with placebo (RR 1.28; 95% CI, 1.24 to 1.31) 1
• Decreased libido: 65.4% with finasteride vs 59.6% with placebo (RR 1.10; 95% CI, 1.07 to 1.12) 1
• Gynecomastia: 4.5% with finasteride vs 2.8% with placebo (RR 1.64; 95% CI, 1.41 to 1.91) 1

Post-Finasteride Syndrome

• Sexual dysfunction may continue after discontinuation of treatment in some patients, including erectile dysfunction, decreased libido, and ejaculation disorders 5
• The European Association of Urology suggests sexual side effects may persist beyond the 2-week DHT normalization period, though post-finasteride syndrome remains controversial 6

Other Adverse Effects

• Breast cancer: Rare cases reported in long-term studies (4 cases in MTOPS, 1 case in PCPT) 5
• Male infertility and poor seminal quality reported rarely; normalization may occur after discontinuation 5

PSA Monitoring Considerations

Critical for prostate cancer screening in patients on long-term finasteride:

• Finasteride lowers PSA by approximately 50% after 12 months of therapy 1
• A multiplier of 2 should be applied to PSA values when screening for prostate cancer 1
• At 3 years, the decline may be greater than 50%, requiring adjustment of the multiplier to 2.3 1
• No specific cut point or change in PSA has been prospectively validated in men taking 5α-reductase inhibitors 1

Discontinuation Considerations

If Stopping Finasteride After 6 Years

• Serum DHT levels increase again when finasteride is discontinued, likely resulting in return of hyperplasia, decreased urine flow, and obstructive symptoms 4
• Prostate volume returns to near baseline values within 12 weeks of discontinuation 2
• The American Urological Association implies effects on reducing intraoperative bleeding persist for weeks after stopping 6
• Patients should not donate blood until 6 months after the last dose due to risk to pregnant females 6

Clinical Decision Algorithm

Continue finasteride if:

• Patient has demonstrable prostatic enlargement (>25 mL) 3
• Symptoms are controlled or improved
• Patient tolerates sexual side effects
• Regular PSA monitoring with appropriate adjustment (×2) is feasible
• Patient understands and accepts the uncertain risk of high-grade prostate cancer

Consider discontinuation if:

• Intolerable sexual side effects develop
• No symptomatic benefit after 6 years
• Patient develops breast changes or other concerning adverse effects 5
• Patient preference after informed discussion of risks/benefits

Reassess at 7 years (the studied duration in PCPT) to determine if continued therapy beyond the evidence base is warranted 1.