Black women with early-stage breast cancer have lower survival rates than their white counterparts even after taking into account variables such as tumor size and socioeconomic differences, researchers said.

“I think it’s due to biological factors in the actual cancer, and this means that race may be a surrogate for a more adverse molecular profile within the cancer,” said Dr. Kathy Albain, the study’s senior researcher and a professor of medicine at Loyola University Chicago Medical Center.

The study, conducted by the Committee on Special Populations of the Southwest Oncology Group that Albain chairs, used databases from two national clinical trials done in the early 1990s.

It matched 317 pairs of women - 317 black and 317 white - who had been treated for early-stage breast cancer with chemotherapy and who had been followed after treatment over 10 years.

The survival rate of the white women after 10 years was 86 percent compared to 76 percent for the black women.

All the women had the same tumor stage and were treated identically. The potential influence of age, tumor differences, education level and socioeconomic status also was considered.

The study then took into account the fact that black women were more likely to have discontinued treatment early, to have missed appointments or delayed treatment and had lower initial white blood cell counts. But they had the same relative doses of total chemotherapy delivered during treatment.

Even after adjusting for all of these variables, the survival rate of black women remained worse.

“What we learned is that treatment factors do not explain the racial disparities in survival outcome for early breast cancer,” Albain told Reuters in a telephone interview.

She said the study highlights the need for research into the genetic makeup of tumors for each patient, and for tailoring treatments to fight more aggressive cancers.

The study was presented late on Friday at the 29th annual San Antonio Breast Cancer Symposium.