Men now have another good reason to consider taking finasteride, a well-known generic drug that shrinks an enlarged prostate and reduces the risk of getting prostate cancer by 25 percent.
A new study from the Southwest Oncology Group strongly suggests that for men at risk of the disease - which strikes one in six men - finasteride also raises the odds that physicians will find fast-growing prostate cancers early, when they are most easily treatable.
“It appears that a man concerned about prostate-cancer risk, who is having a PSA test on a regular basis, will not only reduce his risk of prostate cancer if he takes finasteride, but will help find the cancers that pose the highest risk,” says Ian M. Thompson, M.D., the study's senior author and a urologist at the University of Texas Health Science Center in San Antonio.
The new results, embargoed until 4 p.m. Sept. 11, appear online ahead of print publication Sept. 18 in the Journal of the National Cancer Institute.
"This report provides an important interpretation of results that confounded an overall favorable interpretation of the Prostate Cancer Prevention Trial initially, and should help lessen fears that finasteride somehow causes more aggressive prostate cancer,” says Frank L. Meyskens, Jr., M.D., Southwest Oncology Group associate chair for cancer control and prevention.
The Southwest Oncology Group (SWOG), headquartered at the University of Michigan and one of the nation's largest National Cancer Institute-sponsored clinical trial networks, conducted the study to further analyze data from its National Cancer Institute-sponsored 18,882-man seven-year Prostate Cancer Prevention Trial, which in 2003 found that finasteride was an effective prevention agent. The Food and Drug Administration has not approved finasteride for use in cancer prevention; the drug is approved for treating enlarged prostate.
Four years ago, Southwest Oncology Group researchers closed the Prostate Cancer Prevention Trial (PCPT) early to report very good news. Study results showed that finasteride, commonly used to treat enlarged prostate, could also make a man one-fourth less likely to get prostate cancer.
But that positive overall result — which potentially could keep around 50,000 men from developing prostate cancer each year — was clouded by a troubling finding: Men who took the drug but still developed prostate cancer by the end of the study had higher rates of detected high-grade tumors, an aggressive form of the disease, than did men in the placebo group.
The follow-up study, along with two others published recently, strongly suggests that finasteride makes it easier for physicians to detect high-grade cancers early by improving screening tests and prostate biopsy itself. The two previous studies show that finasteride improves the effectiveness of the two main measures of possible problems: digital rectal examination and the PSA (prostate specific antigen) blood test, which measures hormone changes associated with the disease. In some men who have low PSA test results, cancer is present but not found in time.
“Finasteride makes the PSA test perform better, so we can find the cancer earlier,” Thompson says. “Our current study also shows that by shrinking the prostate gland, finasteride makes a biopsy more sensitive for any cancers that are present.” That increased accuracy is very important, he adds, because if a biopsy reveals a slow-growing cancer but fails to spot a fast-growing one, a doctor and patient may take a “wait and see” approach when prompt treatment is actually needed.