Chances are good that if you hear the term "Breast Cancer," the image it will conjure up is of a female patient with breast cancer—a reasonable association given that the overwhelming majority of breast cancer cases (99%) affect women.
And as regulators note this week, there's a strong association between females and breast cancer when it comes to new drug approvals, too. Companies studying drugs intended to treat breast cancer have "historically" enrolled only women in clinical trials, said Tatiana Prowell, breast cancer scientific lead at the US Food and Drug Administration's Office of Hematology and Oncology Products.
But that has a profoundly negative effect on one population, Prowell notes: Men.
While men only experience about 1% of all breast cancer cases (~2,000 per year), FDA explains that breast cancer has a disproportionately negative effect on men due to several factors. For one, men tend not to associate a lump in their breast tissue with cancer, resulting in delayed diagnosis and treatment.
“You’d think that because men have smaller breasts they would notice a lump instantly,” Prowell wrote. “But men don’t expect a breast lump to be cancer, whereas most women who feel a breast lump immediately assume the worst.”
The other problem—at its core, a regulatory problem—is that most treatments on the market have undergone little testing in men.
"Our data on treatments for men are largely based from trials that were conducted in women, or they are retrospective data from a collection of men who were treated over a period of time," Prowell explains. "We don’t have large randomized trials or high-level evidence for treatment of breast cancer in men as we do for women."
And from the evidence that has been collected, men are known to respond differently to breast cancer treatments than women. "For postmenopausal women, we preferentially use aromatase inhibitors as first-line treatment for early stage breast cancer, and regard tamoxifen as an alternative," Prowell said. "It’s the opposite for men because what data we have suggest that aromatase inhibitors don’t work as well in men. So for men, aromatase inhibitors are usually an alternative or second-line treatment, after tamoxifen."
Prowell said FDA is now "actively encouraging drug companies to include men in all breast cancer trials unless there is a valid scientific reason not to."
"The number of men in breast cancer trials will still be small because male breast cancer is a rare condition, but any information to help men facing this disease is better than none," Prowell concluded.
FDA Consumer Update