A panel of federal health experts unanimously rejected the use of Merck’s Proscar to prevent prostate cancer, saying the drug could actually raise the risk of the most serious types of tumors.

The FDA panel of cancer experts voted 17-0 with one abstention that the drug’s risks outweighed its benefits. The panel is scheduled to vote later on a similar drug from GlaxoSmithKline.

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

However, panelists noted that a small number of men treated with the drugs actually developed more aggressive tumors. Panelists said the risk of increasing deadly tumors outweighed the reduction in tumors that are seldom fatal.

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