Should Finasteride Be Used to Prevent Prostate Cancer? The Debate Continues…
In light of recently diagnosed prostate cancer in celebrity figures, the Atlantic, revisited a story they printed in 1993 on treatments for prostate cancer. A concern, then as now, was the utility of a drug—finasteride—as a potential preventative measure against the development of prostate cancer.
Frustratingly, almost 20 years later the debate still rages. Finasteride was initially prescribed for men who suffer from benign prostate hyperplasia (BPH), a non-cancerous condition of an enlarged prostate that can make urinating difficult—it gained FDA approval for the treatment of BPH in 1992. The drug blocks an enzyme (5-alpha-reductase) that makes a type of testosterone that can cause the prostate to swell and is widely prescribed to treat BPH.
At the time of the original 1993 Atlantic article, researchers had just begun a longitudinal study to examine if blocking 5-alpha-reductase could also prevent prostate cancer. (Early clinical testing indicated that 5-alpha-reductase played a role in prostate cancer.)
The results of that study (The Prostate Cancer Prevention Trial--PCPT) which were presented in 2003, were directional but not conclusive: it pointed out some benefit of the drug in preventing prostate cancer but also found evidence it might also promote tumor growth in some men—a damned if you do, damned if you don’t finding.
Yet, in 2008 when researchers re-examined the data from the PCPT study, as well as doing new investigations on tissue samples used in the original study, they upheld the chemo-preventative findings and downplayed the cancer causing findings. (Chemoprevention is the use of drugs, chemicals, vitamins or other substances in the diet to prevent disease.) Part of the problem of the original PCPT findings that finasteride might cause some men to develop aggressive tumors, according to the NCI website, was that the drug shrank mens’ prostates to a degree that enhanced tumor detection—rather like making it easier to find a needle in a smaller vs. larger haystack. The results also suggested that taking finasteride led to finding these high-grade tumors earlier than would be the case without taking the drug.
At the time of the 2008 review of the original data, PCF-funded researcher, Dr. Christopher Logothetis of the University of Texas M.D. Anderson Cancer Center and a colleague from Eastern Virginia Medical School wrote that “the promise of prostate cancer prevention is a reality.”
Suddenly, “damned if you do, damned if you don’t” took a U-turn. It had become a potential win-win situation. Yet, the whipsawing has left many doctors unsure of which direction to take in prescribing finasteride as a preventative treatment for prostate cancer. A study published in 2010 found that 64% of urologists and 80% of primary care doctors did not prescribe the drug to prevent prostate cancer, with half of the primary care doctors reporting they were unaware it might be useful as a chemoprevention.
Currently, finasteride is not FDA approved for prostate cancer prevention; it is approved to treat BPH and male pattern baldness.
Dr. Ballentine Carter, an internationally recognized expert in the diagnosis and treatment of prostate disease at Johns Hopkins University and a PCF-funded investigator, weighed in this week on what finasteride might mean for patients: “This is a discussion about the risks and benefits of using [finasteride] to prevent prostate cancer and it is far from over.”
Giving any drug as a preventative measure to a healthy population of men carries an especially high burden of proof that it must also do no harm, says Dr. Carter.
“It should be associated with no or little risk, and this may be why the Food and Drug Administration concluded that these drugs should not be approved for primary prevention of prostate cancer,” says Carter. The FDA has taken a similarly cautious approach in approving anti-obesity drugs, preferring to err of the side of caution when prescribing medications to an otherwise healthy population.
It seems clear that more studies on the usefulness of finasteride are needed; in the meantime the risk and benefit of any treatment should be carefully weighed by a patient and his doctor based upon the best available evidence and the unique circumstances of each patient.
Of additional interest:
(In January of this year, the New York Times published an item on a study published in The Lancet that looked at a sister drug to finasteride (dutasteride) that is also used to treat BPH, asking the question: can this drug slow low-risk prostate cancer progression. According to the Times report, dutasteride slowed progression of the disease but the study was small and only followed the men for a short period of time—both serious limitations that will need to be addressed with further research.)