(Reuters Health) - African-American women have worse breast cancer survival than white women in the U.S., and a new study suggests that is largely because black women are less likely to have health insurance.

About 23 percent of black women diagnosed with breast cancer in 2004-2013 had either no health insurance or had Medicaid coverage, versus 8 percent of white breast cancer patients, Dr. Ahmedin Jemal of the American Cancer Society in Atlanta and colleagues report in the Journal of Clinical Oncology.

That insurance difference explained about 37 percent of the excess mortality among black women, the researchers calculated. The next most important factor was actual differences in the tumors, which accounted for 23 percent of the mortality disparity.

Black women’s breast cancer mortality is now 40 percent higher than white women’s, but up until the early 1980s, white women were actually more likely to die after a breast cancer diagnosis, Jemal noted in a telephone interview. That’s because screening for and treatment of breast cancer has been getting better, he explained, but white women have benefited more than black women from these advances.

“What has changed is we have these scientific advances in early detection and treatment, we have mammography, we have adjuvant chemotherapy for breast cancer, we have hormone therapy, we have now even targeted therapy,” Jemal said. “We know that black women are less likely to receive high-quality mammograms, less likely to receive a follow-up after an abnormal mammogram, and are less likely to receive targeted therapy.”

In the new study, Jemal and his team looked at records for 563,497 women ages 18 to 64 who had been diagnosed with early-stage breast cancer, meaning the disease had not spread beyond the breast. Among the more than three-quarters who had hormone-sensitive disease, the risk of dying during follow-up was twice as high for black women as for white women.

Insurance accounted for the largest portion of black women’s increased risk, followed by tumor characteristics, co-existing illnesses (11 percent) and treatment differences (5 percent).

The study looked at younger women because women over 65 are more likely to have similar health coverage under the Medicare program for seniors, the authors note. Indeed, previous research has found smaller disparities in survival among older black and white women and a much larger role for tumor biology in that disparity, they write.

“In this country if you don’t have health insurance you are out of luck,” Jemal said. “It’s a barrier to prevention, early detection and receipt of standard-of-care treatment.”

Many of the women on Medicaid in the current study had been signed up after being diagnosed with cancer, Jamal noted.

“Survival disparities between black and white breast cancer patients are largely driven by differences in insurance,” he said. “Policy makers should make sure that all the scientific advances we have had over the years are accessible to all patients regardless of their socioeconomic status or race or ethnicity.”

“This puts it in black and white, literally, and shows you that there are survival differences that are based on insurance and there are racial differences based on insurance, so if you give people insurance and get them the care that’s needed, you can have an impact and reduce this excess risk,” said Dr. Nina Bickell of The Mount Sinai Hospital in New York, who wasn’t involved in the study.

“The wonder of the Affordable Care Act is it really tried to take a more universal approach to enabling access,” Bickell added, noting that studies are already showing improved health outcomes in states that have opted for Medicare expansion.

“What’s so important about this study is that it’s showing that when you gain access via coverage, via insurance, you can improve survival,” she said in a telephone interview. “One can only hope,” she added, that the new findings will help build public support for continuing the Affordable Care Act, rather than dismantling it.

SOURCE: bit.ly/2xOFbfX Journal of Clinical Oncology, online October 16, 2017.