Background: In 1992, finasteride, a 5α-reductase inhibitor, was approved by the Food and Drug Administration (FDA) for the treatment of benign prostatic hyperplasia (BPH). Finasteride also showed early signs of lowering prostate-specific antigen (PSA) levels, indicating that it may be useful for the prevention of prostate cancer. The Prostate Cancer Prevention Trial (PCPT) was conducted from 1994 to 2003 and showed that finasteride reduced overall prostate cancer incidence; however, it also appeared to increase the incidence of high-grade disease. Consequently, in 2011 the FDA issued a black box warning based in part on the PCPT results. Little is known, however, about the effect this warning had on finasteride use among men after 2011. The purpose of this study was to assess the use of finasteride, for BPH or other reasons, among a sample of Prostate, Lung, Colorectal, Ovarian Cancer Prevention Trial (PLCO) participants. Specifically, we wanted to assess the effects of sociodemographic characteristics (e.g., age, race/ethnicity) and BPH on finasteride use and the effect of the FDA's black box warning on finasteride use after 2011.

Method: This was a retrospective longitudinal study. Men's age, race/ethnicity, and BPH status were ascertained from questionnaires. Medication use was ascertained from linkage to Medicare Part D claims data from 2010 to 2014.

Results: The sample contained 14,044 PLCO men with at least one year of part D claims data. The majority self-identified as non-Hispanic white (12,429; 88.5%); 236 (1.7%) were black, 753 (5.4%) were Asian, and 239 (1.7%) were Hispanic. Median (25th/75th) age in 2010 was 73 years (69/28). From 2010 to 2014, 11% (n=1,590) of these men used finasteride at any time. Overall, 63% (n=1,005) of the men who used finasteride reported a diagnosis of BPH. Finasteride use increased steadily over time from 5.5% in 2010 to 8.5% in 2014.

Conclusion: Overall use of finasteride from 2010 to 2014 was low, and mainly in men with BPH. Finasteride use increased after the FDA's 2011 black box warning; the effect of the warning is unclear.

Citation Format: Jarrett A. Johnson, Paul F. Pinsky. Use of finasteride in the Prostate, Lung, Colorectal and Ovarian Cancer Prevention (PLCO) Trial cohort: Effects of sociodemographic factors and a black box warning [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr A071.