A re-evaluation of the largest prostate cancer prevention study says that aggressive treatments including the use of finasteride may help in prostate cancer prevention.
This study also highlights the role of prostate specific antigen (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.
Using advanced statistical modeling techniques and a complete assessment of prostate tissue biopsies, researchers found that finasteride reduced the risk of developing prostate cancer more than they had originally thought, it did not increase the development of more aggressive cancers, and the majority of tumors prevented were those that could spread and cause death.
Ian M. Thompson, senior author on both studies, said that these new findings suggest men should take an 'individualized' approach to prostate cancer prevention.
"Because we now know that men with even low PSAs can develop prostate tumors, if a man is worried about his risk, regardless of PSA score, he can take an agent that is now proven to be effective in lowering that risk," Thompson said.
Researchers examined whether finasteride actually increased aggressive cancers in some men, and by studying biopsies and prostate gland tissue that had been removed, but found that it did not.
"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 Mary Redman, Ph.D., a biostatistician at the Fred Hutchinson Cancer Research Center.
"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," Redman added.
Redman found that in addition to a 25 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.
The second study examined whether the cancers detected in the men in the trial who had a low PSA level had clinically significant disease.
With about 75 percent of the tumors detected on the study were classified as those which could potentially take a man's life, researchers concluded that there is no clear-cut PSA threshold that can be considered normal.
All patients in the study were to have a biopsy of their prostate gland at some point during the seven-year trial, so investigators evaluated characteristics of the biopsy in relation to each man's PSA score.
Current practice is to consider a PSA score of below four as normal and above four as abnormal.
According to lead author Scott Lucia, M.D., a pathologist at the University of Colorado, Denver, what the researchers found was that while a large majority of the participants diagnosed with prostate cancer had a PSA that was considered normal, 72 percent of all tumors diagnosed from biopsies in both treated and untreated men were considered significant.
He said that the finding of significant disease couldn't be predicted by the PSA score.
Most patients in the study who had a PSA score of four or less and then had prostate cancer diagnosed by a routine biopsy were found to have significant prostate cancer, while some men who had a high PSA were found to have insignificant cancer.
Lucia said that doesn't mean that the researchers support reducing the level by which PSA scoring should trigger therapeutic intervention.
Researchers said that it means that men need to speak with their physicians about their PSA, when they should be biopsied, and about potential use of finasteride, which can reduce their risk, so that they will make a decision that is right for them.
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.