SAN FRANCISCO—After 25 years, the verdict is in on finasteride. The latest data from the landmark Prostate Cancer Prevention Trial (PCPT) allay earlier concerns that the 5-alpha-reductase inhibitor promotes lethal prostate cancer (PCa). Finasteride significantly reduces a man’s risk for PCa and is safe long-term. Principal study investigator Ian Thompson, Jr., MD, president of CHRISTUS Santa Rosa Hospital Medical Center in San Antonio, delivered the “transformational” findings at the 2018 American Urological Association Annual Meeting.

The PCPT, one of the largest cancer prevention trials, randomized 18,882 men from 1993 to 1997 to finasteride or placebo. The trial intervention was stopped in 2003 when investigators found finasteride reduced overall PCa risk by 25%, but also increased the risk for high-grade disease. This negative finding resulted in a “black box” warning from the FDA in 2011. 

Subsequent SWOG analyses of PCPT data revealed unexpected benefits of finasteride. It improved detection of significant PCa, including high-grade tumors. Additional analysis showed that study participants enjoyed the same longevity whether they received finasteride or placebo. Still, despite these benefits, the black box warning had an impact. Few men today take the inexpensive generic drug to lower their cancer risk.

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As part of their follow-up investigation, Dr Thompson and colleagues revisited the study and matched participants to the National Death Index, a centralized database of death records at the Centers for Disease Control and Prevention. With almost 300,000 person-years of follow-up and a median follow-up of 18.4 years, they found 42 deaths due to PCa in the finasteride arm and 56 in the placebo arm.

“What we ultimately found were fewer prostate cancer deaths with finasteride, demonstrating with prolonged follow-up that there was no greater risk of prostate cancer death with the drug, just fewer cancers,” Dr Thompson told Renal & Urology News.

These findings could benefit tens of thousands of men each year in the United States, he said.  PCa treatment is costly and it can have serious side effects, such as impotence and urinary incontinence. “Urologists and their patients can now rest easy that these initial concerns regarding high-grade tumors are unfounded. Additionally, for a man who asks his physician, ‘How can I prevent prostate cancer,’ the physician can now tell him with confidence that there is a proven method to reduce his risk of this common disease.”

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Scott Eggener, MD, Professor of Surgery (Urologic Oncology) at the University of Chicago Medicine, agreed these data reassure that long-term finasteride use does not increase rates of higher-grade PCa. Initially there was a debatable increased risk of higher-grade cancer 0.5% (1 in 200 men), which has largely been debunked by follow-up studies within PCPT and from other cohorts. “Although not integrated into guidelines at this point, clinicians should feel comfortable prescribing finasteride to a man with a large prostate, significant urinary symptoms from prostate obstruction, and an elevated PSA level as long as prostate cancer has been ruled out,” Dr Eggener said.

Frank J. McGovern, MD, a urologist at Massachusetts General Hospital in Boston, believes the latest findings clear up the controversy. “The data have been worked front, back, and sideways with multiple different conclusions,” Dr McGovern said. “It is a relief to get these data. There are men that have held back from taking it because of their concern about developing an aggressive tumor.  This will allow men who need to be on it to take it without fear.”