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A comprehensive re-evaluation of the Prostate Cancer Prevention Trial by researchers in the Southwest Oncology Group has produced new findings that suggest men and their doctors should take another look at the use of finasteride to prevent the development of prostate cancer.
The seven-year PCPT study randomized 18,822 men to receive a placebo or finasteride, a baldness drug, approved to control prostate growth. Published in 2003, results from this largest prostate-cancer prevention study ever completed showed that finasteride reduced prostate-cancer risk by 25 percent. However, the results also showed finasteride appeared to increase development of more aggressive prostate cancer in some men. Because of this finding and concerns that tumors detected had low prostate specific antigen (PSA) values and might be of little risk to patients, few doctors since have recommended finasteride for prostate-cancer prevention.
In the new study, researchers analyzed PCPT data using advanced statistical modeling techniques and a complete assessment of prostate-tissue biopsies. They looked at whether finasteride increased aggressive cancers in some men and concluded the following:
- finasteride actually reduced the risk of developing prostate cancer more than had been originally thought,
- it did not increase development of more aggressive cancers, and
- the majority of tumors prevented were those that could spread and cause death.
“Finasteride actually shrank the prostate gland, so it appeared in initial studies that more cancer was being found in biopsies of men who took the drug,” said Dr. Mary Redman, a SWOG biostatistician. “What that means is that the cancer took up more prostate tissue in men who were treated, and that is why it was easier to find in a biopsy. Cancer was probably missed more often in biopsies of men on a placebo drug because the prostate gland itself was larger,” she said.
Redman found that in addition to a 25 percent to 30 percent reduction in prostate-cancer development overall in men taking finasteride, there was no evidence that the drug increased the rate of aggressive tumors and likely decreased their rate by 27 percent. “We think men should not be concerned about finasteride increasing their risk of these aggressive tumors,” she said.
A pathologic analysis of that same study sheds light on the significance of the cancers found in that study. Additionally, this study highlights the role of PSA scores in treatment decision-making. Researchers found that even those men who have a low PSA screening value can have cancer that is difficult to cure.
The two studies will be published online in advanced of the June 2008 issue of Cancer Prevention Research, a journal of the American Association for Cancer Research.
[Adapted from a news release from the American Association for Cancer Research.]