Finasteride is a 5-alpha reductase inhibitor prescribed for managing prostate health conditions. It is commonly prescribed for men dealing with an enlarged prostate, medically termed benign prostatic hyperplasia (BPH), and also for male pattern baldness.
How Finasteride Works
Finasteride targets a specific enzyme, 5-alpha reductase, found in the prostate and hair follicles. This enzyme converts testosterone into dihydrotestosterone (DHT). DHT is a potent androgen that plays a significant role in the growth and development of prostate gland cells.
By blocking 5-alpha reductase, finasteride reduces DHT levels in the prostate and bloodstream. This reduction causes the prostate gland to shrink, which can alleviate urinary symptoms associated with BPH. A study observed a 27% reduction in prostate gland volume over 36 months.
Use in Prostate Cancer Prevention
Finasteride has been studied for prostate cancer prevention, notably in the Prostate Cancer Prevention Trial (PCPT). This large trial involved nearly 19,000 men aged 55 and older and lasted for seven years. The PCPT demonstrated that finasteride reduced the overall risk of prostate cancer diagnoses by approximately 25% to 30% compared to a placebo. This reduction was mainly attributed to a decrease in low-grade prostate cancers.
Initial findings from the PCPT, reported in 2003, indicated a higher incidence of high-grade prostate cancers in the finasteride group. This led to concerns and an FDA warning regarding the potential risk of more aggressive prostate cancer. Subsequent analyses suggested this apparent increase was likely due to improved detection. Finasteride shrinks the prostate, potentially making existing cancers, including high-grade ones, easier to detect during biopsies.
Long-term follow-up data from the PCPT, extending to 18 years, showed comparable prostate cancer-specific mortality rates between the finasteride and placebo groups. This suggests that despite earlier concerns, finasteride did not increase the risk of dying from prostate cancer. While not FDA-approved for prostate cancer prevention, finasteride may be considered for men at higher risk, especially those with elevated PSA levels, as it has shown to reduce the incidence of prostate cancer.
Addressing Prostate Cancer Diagnosis
Finasteride is generally not used as a primary treatment for existing prostate cancer. Its mechanism, which involves reducing DHT levels and prostate size, does not directly kill cancer cells. The drug’s role is distinct from therapies aimed at eradicating diagnosed malignancies.
There are limited contexts where finasteride might be relevant for men with a prostate cancer diagnosis. For instance, in men diagnosed with localized prostate cancer on active surveillance, finasteride is being investigated to help them continue this approach longer. This aims to manage BPH symptoms while potentially slowing the progression of low-risk cancers, as prostate cancer typically depends on testosterone for growth.
Finasteride can also influence prostate-specific antigen (PSA) levels, routinely used in prostate cancer screening and monitoring. The medication typically reduces serum PSA levels by about 50% within the first six to twelve months of use. This effect requires careful interpretation of PSA results in men taking finasteride, as a seemingly normal PSA level might be artificially lowered, potentially masking an underlying cancer. Conversely, a rising PSA level in a man on finasteride could be a more accurate indicator of cancer, as the drug would typically cause a decrease if only BPH or inflammation were present.
Potential Side Effects and Patient Selection
Finasteride use can lead to several side effects, with sexual side effects being among the most commonly reported. These include decreased libido (sex drive), erectile dysfunction, and a reduced volume of ejaculate. These sexual side effects have been reported to affect approximately 2-15% of users. While these effects often resolve upon discontinuing the medication, they may persist for an extended period, sometimes referred to as post-finasteride syndrome.
Other side effects include breast tenderness and enlargement, also known as gynecomastia. The likelihood of breast-related side effects may increase with longer treatment duration. Any breast changes should be reported to a healthcare provider. Less common side effects include depression, anxiety, testicular pain, and skin rash.
Patient selection for finasteride should involve a thorough discussion with a healthcare provider. This conversation should cover individual risk factors for prostate cancer, the benefits of finasteride in prevention, and its possible side effects. Clinicians may consider finasteride for men with elevated PSA levels, for example, those with PSA greater than 1.3 or 2 ng/mL, to reduce the risk of biopsy-detectable prostate cancer. Regular monitoring, including PSA testing, is important during treatment, with adjustments made to interpret PSA levels accurately due to the drug’s effect on this marker.