Charlotte, N.C. – Jeanette Meachem speaks out about breast cancer today because her younger sister, Joye Jordan, did not.

When Jordan, a single mom in her late 20s, found a lump in her breast, she went to a doctor who told her she was too young to have breast cancer and probably just had "lumpy breasts."

She didn't see a doctor again until she was 31. By then she had health insurance, but cancer had spread beyond her breast. Jordan died about a year later, just after she turned 33.

"We have to speak up for ourselves and be our own advocates," said Meachem, 45. "Being silent can kill you."

Meachem's story illustrates the disparity in breast cancer deaths between black and white women. The Centers for Disease Control and Prevention put the problem in stark terms in a 2012 report called "Vital Signs":

• Although black women have a lower incidence of breast cancer overall, they are 40 percent more likely to die from breast cancer than white women.

• Despite advances in screening and treatment over 30 years, many black women don't get diagnosed until their cancers are late-stage and harder to treat.

• Even though black women get screening mammograms at the same rate as white women, black women are less likely to get prompt follow-up care after abnormal mammograms, and fewer get the treatment they need after they're diagnosed.

In North Carolina, Mecklenburg County Health Director Dr. Marcus Plescia, who previously worked at the CDC and co-authored the report, called it an indictment of our "bewildering" health care system.

People "don't really understand what the options are, and they have a very hard time figuring out how to access what they need," he said. "We don't have highly organized follow-up systems that we ought to have."

Many factors — from socioeconomic conditions to heredity — are blamed for the disparities in treatment and outcomes. Because there are likely multiple causes, there continues to be uncertainty in the medical community over which factors are more significant.

Some research is focused on genetics, since studies show black women who get breast cancer are often diagnosed with a more aggressive type, known as "triple negative."

Others place more emphasis on social, environmental and historical factors that affect many black Americans, such as lack of insurance, lower income, poor health and distrust of the health care system.

Until research clears up the mystery, Dr. Otis Brawley, chief medical officer of the American Cancer Society, pushes for more attention to "socioeconomic things that start adding up and become reasons for the disparity."

"The one thing we do know is that we have a bunch of people who call themselves black who get less than optimal care," Brawley said. "That's a logistical issue we can fix."

Among those studying the biology of breast tumors is Dr. Lisa Carey, chief of the division of hematology and oncology at the University of North Carolina Chapel Hill's medical school.

In a 2013 study, Carey and her co-authors said "survival differences persist between blacks and whites [even when] diagnosed at similar stages of illness." Carey was one of the first researchers to point out, in a 2006 study, that black women are at "substantially higher risk" of developing the aggressive "triple-negative" breast cancer than white women.

Although Carey believes biological differences are part of the reason for disparities, she agrees with the cancer society's Brawley that they could be only a minor part.

"It may have everything to do with black women not [having access] to good health care in general," she said.