It’s a call to action that might make even the most seasoned oncologist do a double take. The Food and Drug Administration (FDA) is urging drug companies to include an unexpected—and vanishingly small—demographic in future breast cancer clinical trials: men.

Over the years, male breast cancer hasn’t attracted a legion of activists and advocates in the fashion of female breast cancer. “Male breast cancer [has] never had an important lobby,” Dr. Marleen Meyers, an assistant professor specializing in breast cancer at NYU Langone Medical Center in Manhattan, told The Daily Beast. “[It’s] a less known and less spoken about breast cancer.”

The disparity is directly correlated to numbers: Breast cancer is about 100 times less common among men than among women, according to officials at the National Cancer Institute. In 2014, an estimated 2,360 men in the United States will be diagnosed with invasive breast cancer, resulting in about 430 deaths, officials added. That’s fewer deaths each year those caused by meningitis or asthma.

But the limited pool of victims has heightened the burden on those affected. With males comprising just 1 percent of diagnosed breast cancer cases in the United States each year, men are seldom included in clinical trials and research—meaning males being treated have a startlingly small pool of data on their side.

The FDA is hoping to remedy the dearth of knowledge with a plea aimed at influential drugmakers.

“Men have historically been excluded from breast cancer trials,” said Dr. Tatiana Prowell, a breast cancer scientific lead at the FDA’s Office of Hematology & Oncology Products, on the FDA’s website this past June. “We are actively encouraging drug companies to include men in all breast cancer trials unless there is a valid scientific reason not to.”

The lack of males is a departure from the many clinical trials where men are well represented, Dr. Prowell told The Daily Beast. And it’s a departure with pernicious side effects. While males and females generally respond to the same chemotherapy or radiation regimens, Dr. Prowell notes it’s possible that successful treatments could differ between genders.

“We won’t know until more men are included in breast cancer clinical trials,” she said.

Male exclusion is particularly problematic at a time when many modern and promising breast cancer drugs are available only through trials, according to Dr. Meyers. “Because of the uncertainty about the hormonal involvement in breast cancer, I think a lot of researchers have not included males,” she added, sounding off on other reasons for past exclusion.

While the survival rate, stage-for-stage, is similar for males and females, men do face a unique set of problems, Dr. Meyers continued. “The biggest problem with male breast cancer is not being aware [until] a later stage. In addition, because males do have less breast tissue, if the tumor is not picked up right away there might be a greater risk of locally advanced breast cancer—which carries a poor prognosis.”

Increased male enrollment in clinical trials might redress another issue, too: awareness. “There’s more of a stigma for men to report anything in their breast,” Dr. Meyers said. “[Men] aren’t really thinking ‘breast cancer’ when they feel a lump.”

The FDA’s hope to proactively steer drugmakers is somewhat surprising, according to Dr. Meyers. “It’s not something we see very often, particularly in oncology trials,” she said. “It has happened in the past, but it’s not a particularly common event.”

The FDA’s insistence dovetails their ongoing policy of encouraging the inclusion of patient subgroups in clinical trials, Dr. Prowell explained. “Just as the FDA, NIH, and other organizations encourage accrual of all underrepresented populations in trials—women, racial minorities, and children, for example—we have begun routinely encouraging companies to include men with breast cancer in breast cancer trials.”