Approximately 221,000 breast cancers were diagnosed in women of any race each year during the period from 2009 through 2013. Between 2010 and 2014, about 41,000 deaths from breast cancer occurred each year. Comparing the figures for African-American and European-American women, the team discovered some welcome news.
Between 2010 and 2014, death rates decreased by slightly more than 2% for black and white women younger than age 50.
"We've always known that black women have more aggressive breast cancer and do more poorly," Richardson said. "The challenge has always been what is causing it or what is the molecular or gene defects we are looking for."
Black women often diagnosed later
Dr. Deepa Halaharvi, a breast cancer surgeon with OhioHealth Breast and Cancer Surgeons, explained that triple-negative breast cancers, which account for 10% to 20% of all diagnosed breast cancers, occur more often in black women than white women. These aggressive cancers return negative results when tested for factors related to the hormones estrogen and progesterone as well as the protein HER2. As a result, triple-negative breast cancers do not respond to all therapies.
"If you catch them early on, we have really good chemotherapy agents that we can use to treat them," Halaharvi said. "But the thing is, you have to catch the cancer early on. You have to catch it in the really early stages."
Examining death rates more closely, the CDC researchers discovered that some racial disparities still existed.
Although deaths decreased for all women over time, a slightly faster rate of decline occurred for white women than black women from 2010 to 2014. White breast cancer patients, as a group, experienced a decline in deaths of 1.9% per year, compared with 1.5% per year for black women.
Halaharvi, who was not part of the CDC research team, believes the differences in regional cancer rates highlighted in the new report provide an explanation for the disparity.
"Local cancer is just in the breast; regional has gone to the lymph nodes," she explained, noting the researchers discovered that more black women (34%) than white women (28%) are diagnosed with regional breast cancers.
"What that tells you is African-American women are getting diagnosed at much later stages," Halaharvi said. One possible reason: They may be neglecting their mammogram screenings, she said.
Cancer can usually be found at a much earlier stage when screening guidelines are followed: All women, beginning at 50, need to get a mammogram every other year, while women with a family history of breast cancer should consult with their doctors about earlier mammograms, according to US Preventative Services Task Force
That said, it is an individual decision, and women who are between the ages of 40 and 49 should talk to their doctor about when to start and how often to get a mammogram, the task force suggests.
Incidence rates are converging
Another significant finding: Although black women have had lower rates of breast cancer compared with white women since 1975, the rates have recently converged, becoming nearly equal. About 122 black women out of every 100,000 were diagnosed with breast cancer, compared with about 124 white women out of 100,000.
These nearly equal numbers, the researchers say, are mostly caused by increasing breast cancer rates among black women.
"The increases are not in every age group," Richardson said, adding that the predominant increase in diagnoses occurred in black women between the ages of 60 and 79.
"The thing that seems to drive breast cancer is total exposure to estrogen over a lifetime," she said. She explained that being overweight is key since "fat tissue actually makes estrogen, and that's why the risk gets higher in women that are postmenopausal."
"We are starting now to look at lifetime overweight and obesity," Richardson said. "Overall, African-American women and other minority groups tend to be more overweight over the lifespan."
Though on the surface, a higher rate of cancer does not look good, Halaharvi sees this as a possible positive. She said the increasing rate suggests that black women may have begun to heed the call to screen for breast cancer: Higher rates mean more women are being screened for cancer.
Richardson noted that not only greater awareness of breast cancer but better technologies may have led to more diagnoses within the black community.
"I do think that women are more aware," she noted, "but screening tests have improved as well, which means we find things now that we didn't used to find on mammograms 20 years ago."
Overall, she said, breast cancer screening is "a more normal type activity for women to undergo" these days, whether a woman is black or white.
How to make gains
Why does this new research primarily focus on black and white women?
"Black women continue to have the highest mortality rate from breast cancer, followed by white women," Richardson said, explaining that in order to make the most gains, it is necessary to get black women "the treatment and all the services they need to keep the rate going down."
Noting that October is Breast Cancer Awareness Month, Halaharvi could not refrain from dispensing additional advice: "Know your breasts; know what's normal for you. If there's a mass that feels like a rock-hard marble, go see your doctor. ... If your doctor is not listening to you, go find a doctor who listens to you."
Above all else, she said, women need to talk to their health care providers about mammograms.