Aug 13, 2010 - 11:53 pm
Erroneous fear that finasteride spurs more aggressive tumors has left some physicians wary, research shows
Under the name Proscar, finasteride is commonly prescribed to treat the non-cancerous condition called benign prostatic hyperplasia, also known as enlarged prostate. Finasteride is also sold under the brand name Propecia, to help treat male pattern baldness.
In 2003, the Prostate Cancer Prevention Trial (PCPT), involving more than 18,000 patients, found that finasteride cut the incidence of prostate cancer by 25 percent -- the first drug to do so.
But a much-publicized follow-up analysis undercut that good news when it suggested that the drug might actually boost the odds of particularly aggressive prostate tumors.
At the time, "there was a concern that [finasteride] may have made worse the number of cases of more severe prostate cancer," explained the lead researcher of the new study, Dr. Linda Kinsinger, chief consultant for preventive medicine at the Veterans Health Administration National Center for Health Promotion and Disease Prevention in Durham, N.C.
Upon a re-analysis of the data, however, that uptick in risk for more aggressive tumors turned out to be false: finasteride did not raise the risk for an aggressive tumor, it simply helped make prostate screening more sensitive, so these tumors were spotted more readily.
But the reassuring results of that 2008 re-analysis may not have trickled down to doctors and patients today, Kinsinger's team reports in the September issue of Cancer Epidemiology, Biomarkers & Prevention.
Instead, too many doctors remain wary of prescribing finasteride, so the numbers of prescriptions written to help prevent prostate cancer hasn't budged for years.
That's unfortunate, Kinsinger said, because "there does seem to be a benefit and it could be more widely used."
In the study, her team surveyed 325 urologists and 1,200 primary care doctors on their prescribing practices.
Among the doctors surveyed, 57 percent of urologists and 40 percent of primary care physicians said they prescribed finasteride more often, but only 2 percent said the PCPT trial results had influenced their decision.
Moreover, 64 percent of urologists and 80 percent of primary care physicians said they never prescribed finasteride with the aim of helping to prevent prostate cancer.
Asked why, 55 percent said they were worried about the risk of the drug causing high-grade tumors, while 52 percent said they simply had no idea that finasteride could be used to prevent prostate cancer.
The study was funded by the VA National Center for Health Promotion and Disease Prevention and the U.S. Department of Defense - Prostate Cancer Research Program.
Although the doctors in the survey all came from the VA medical system, Kinsinger said these results most likely mirror what is happening throughout the United States.
Besides doctors being poorly informed about finasteride, patients' psychology probably plays a role as well, Kinsinger said. "As a healthy person, why should I pay to take a drug that has some chance of causing me side effects to prevent something that I may or may not get down the road?" she said. "I think that's a tough sell."
Another problem with the drug is who would benefit from taking it, Kinsinger said. Men most likely to benefit from finasteride are those at highest risk from prostate cancer, such as men with a family history of the disease, she explained.
"But we are not very good at narrowing the universe of men down to the subset of those who are actually at higher risk of developing prostate cancer," Kinsinger said. "If we could develop a means of identifying people who are truly at the highest risk for developing prostate cancer that would ideally be the target group, but we don't really know who those people are yet."
Prostate cancer expert, Dr. Anthony D'Amico, chief of radiation oncology at Brigham and Women's Hospital in Boston, agreed that the fear of adverse consequences of finasteride has made doctors reluctant to prescribe it.
"The bottom line is that despite all the well-designed and well-thought-out studies to explain why high-grade prostate cancer was increased, while low-grade prostate cancer diagnoses decreased with finasteride use in the PCPT, physicians remain hesitant to prescribe finasteride as a preventive agent," he said. "And so the observation in the VA system in the current study supports the sentiment I have heard when traveling around the country and teaching on this topic."
So the path forward may be difficult, he said.
"The way it's thought of is 'If I take this drug I am going to prevent a prostate cancer that may or may not need treatment. I am going to increase my risk, to a very small degree, of a cancer that may not be curable,'" he said. "And that's how people read it."