FDA panel rejects drugs to prevent prostate cancer


The Food and Drug Administration panel of cancer experts voted 17-0 with one abstention that the risks of Merck's Proscar outweighed its benefits. In a similar vote, the panel voted 14-2 with two abstentions against GlaxoSmithKline PLC's Avodart. Both drugs are already approved to treat enlarged prostate.

"In a setting like this, the onus is on the drug to be completely safe, and to show benefit, and I don't think it reached that level," said panel Chairman Dr. Wyndham Wilson, of the National Cancer Institute.

The FDA is not required to follow the panel's advice, but often does.

Studies by both companies showed their drugs decreased incidence of low-grade prostate tumors by nearly 25 percent.

However, panelists voiced concern that a small number of men taking the drugs actually developed more aggressive tumors, compared with patients taking a dummy pill. Panelists said the risk of increasing deadly tumors outweighed the benefit of reducing tumors that are seldom fatal.

According to figures from the FDA presented Tuesday, for every 60 men treated with Avodart for four years, one serious case of prostate cancer would be prevented. But for every 200 men treated during the same timeframe, one would develop a high-grade tumor.

The head of FDA's cancer drugs division stressed that the drugs must be held to a higher standard than traditional cancer drugs because they would be used in healthy men.

"We're talking about treating potentially hundreds of thousands of people who don't have a disease, as opposed to a small cohort of patients with a disease who need treatment options," said Dr. Richard Pazdur, director of FDA's office of oncology drug products.

Panelists said it was unclear whether the drugs actually cause the higher-grade tumors or simply make them more difficult to detect. Both Avodart and Proscar shrink the size of the prostate and reduce a key protein used to screen for prostate cancer. Additionally, low-grade tumors are often an early warning sign that leads to increased screening of patients, and eventually the detection of more serious tumors.

Currently there are no drugs approved to prevent prostate cancer.

Doctors screen for prostate cancer using physical exams, imaging scans and tests that measure prostate serum levels. Treatment for the disease can include surgery to remove tumors, radiation therapy or chemotherapy.

Glaxo and Merck argued Tuesday that by reducing low-grade tumors their drugs could reduce unnecessary biopsies - a procedure where a tiny tissue sample is removed and tested for cancer. About 650,000 men had prostate biopsies last year and 70 percent of the tumors sampled were low-grade, according to Glaxo.

But a majority of panelists said reducing biopsies was not good enough.

"I do not see that there was any benefit to this drug in terms of long-term cancer," said Wilson. "The benefit that was put forward was that it reduced the number of patients who might go onto surgery."

Glaxo has asked the FDA for permission to market Avodart as a preventive measure against prostate cancer, while Merck simply wants to add information about reducing prostate cancer to the label of its drug Proscar.

The Associated Press