Patients who take finasteride before being diagnosed with prostate cancer tend to have more advanced and aggressive disease, as well as lower overall survival, according to a large, national study.

The study, “Association Between Finasteride use Prior to Prostate Cancer Diagnosis and Prostate Cancer-Specific Survival,” was presented at the recent American Society for Radiation Oncology 2018 Annual Meeting.

Finasteride, marketed under the brand names Propecia and Proscar, is frequently used to treat hair loss and prostate gland enlargement. Although prior research indicated it may also reduce the risk of low-grade prostate cancer, patients taking finasteride who develop prostate cancer seem to have more aggressive disease.

Aiming to determine if finasteride is associated with increased prostate cancer-specific mortality (PCSM), a team from the University of California San Diego examined data from 111,933 prostate cancer patients included in the national Veterans Affairs database.

Participants had been diagnosed between 2000 and 2015, and 11,085 of them had taken finasteride before diagnosis.

The investigators conducted a thorough evaluation of patients’ sociodemographic data, including their marital status, employment status, age, race, ZIP code, income, education, and body mass index, as well as alcohol and tobacco use. The Charlson comorbidity index score — which predicts 10-year survival in patients with multiple conditions — was also recorded.

Patients’ prostate cancer stage was then defined according to whether the tumor was primary (T category); whether it had spread to nearby lymph nodes (N category); whether or not it had distant metastasis (M category); Gleason score; and concentration of prostate specific antigen (PSA), a commonly used indicator of prostate cancer risk.

The researchers also assessed use of hormone therapy and treatment with radiation therapy or surgery. Median follow-up was 6.3 years. PCSM, overall survival, and non-cancer mortality were compared.

Compared with patients who had not taken finasteride before diagnosis, those who had were more likely to have clinical T3-4 (5.44% vs. 3.45%), which means cancer growth outside the prostate, including seminal vesicles, urethral sphincter, rectum, bladder, or the wall of the pelvis, but not to lymph nodes.

Patients previously on finasteride were also more likely to have their tumor spread into lymph nodes (3.53% vs. 1.86%), metastasis (7.35% vs. 3.14%), and Gleason score 8-10 — cancers likely to spread more rapidly — (24.79% vs. 16.13%).

Additionally, more patients who had taken finasteride died due to prostate cancer, or due to all causes. However, non-cancer related deaths were similar among the two groups. The differences were maintained when researchers examined patients in subgroups according disease stage.

“Prostate cancer patients who took finasteride prior to diagnosis presented with higher stage and grade disease,” the team wrote. Further studies are needed to validate these findings, they cautioned.