"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 Dr. Ian M. Thompson, the study's senior author and a urologist at the University of Texas Health Science Center in San Antonio.
Although Finasteride is approved for treating enlarged prostate, the Food and Drug Administration has not approved it for use in cancer prevention.
Experts feel that the study published in the online edition of the Journal of the National Cancer Institute will help allay fears about the possible harmful effects of Finasteride.
"This report provides an important interpretation of results that confounded an overall favourable interpretation of the Prostate Cancer Prevention Trial initially, and should help lessen fears that Finasteride somehow causes more aggressive prostate cancer," says Dr. Frank L. Meyskens, Jr., Southwest Oncology Group associate chair for cancer control and prevention.
The Southwest Oncology Group (SWOG), headquartered at the University of Michigan, conducted the study to further analyse 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.
Four years ago, the researchers had closed the Prostate Cancer Prevention Trial (PCPT) early, after finding that Finasteride could help reduce a man's likelihood of getting prostate cancer by 25 per cent.
The positive result was, however, clouded by the finding that men who took the drug but still developed prostate cancer by the end of the study had an aggressive form of the disease, as compared to men in the placebo group.
Now the follow-up study, coupled 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—namely digital rectal examination and the PSA (prostate specific antigen) blood test, which measures hormone changes associated with the disease.
"Finasteride makes the PSA test perform better, so we can find the cancer earlier. Our current study also shows that by shrinking the prostate gland, Finasteride makes a biopsy more sensitive for any cancers that are present," Thompson says.
He says that the increased accuracy is very significant, for 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.
Thompson believes that men should be told routinely about the potential benefits of Finasteride when they come to the doctor's office for a PSA test, in much the same way patients at risk of heart disease are told about the benefits of statin drugs.
The study's authors though do not entirely rule out the possibility that Finasteride may have led to high-grade prostate cancer in some men in their previous study, they insist that there was no evidence that the drug caused changed in tumour composition that might contribute to aggressive cancer.