Breast Tumors in Black Women Have More Abnormal DNA

WASHINGTON—Black women have long been known to suffer higher breast cancer mortality and to experience worse 5-year survival rates than whites. Even controlling for disease stage, they are more likely to fail treatment and have worse outcomes, said Lisa A. Newman, MD, MPH. The question therefore arises, she said, whether these differences reflect biological variation or social inequality.

Dr. Newman is associate professor of surgery, Wayne State University, and associate director, Alexander J. Walt Comprehensive Breast Center of the Barbara Ann Karmanos Cancer Institute, Detroit.

Speaking at the 8th Biennial Symposium on Minorities, the Medically Underserved, and Cancer, Dr. Newman reported data "strongly" implying that those differences do not derive solely from socioeconomic disparities. Rather, she said, pathological and flow cytometry comparisons of tumors in black and white women suggest that tumors in black women proliferate and accumulate abnormal DNA more rapidly than tumors in white women.

Dr. Newman described a study comparing the proliferative indices of breast tumors from 347 blacks and 184 whites. The women constituted a consecutive series of patients undergoing surgery over a 5-year period in the same comprehensive cancer center, one "ideally suited" for this comparison because it serves a large black population, she said.

Although the mean ages of the two groups were comparable, 57.6 years for black women and 57.8 for whites, nearly twice the percentage of black women (11% vs 5% of the whites) were younger than 40. This "age distribution is hard to explain on the basis of socioeconomic factors revealed by the study," Dr. Newman said, adding that researchers have found a "similar younger age distribution in native African breast cancer patients."

The black women also had significantly larger tumors than the white women, with a mean tumor size of 3.8 and 3.1 cm, respectively. In addition, the tumors in black women were more advanced in stage and significantly more likely to be negative for estrogen receptors (53% vs 47% for white women) and progesterone receptors (59% vs 41% for white women).

The higher S-phase fraction of 11.4% in black women, compared with 9.6% in white women, is also prognostically unfavorable, she said. The lymph-node-negative and estrogen-receptor-negative patients showed the largest ethnic differences in mean S-phase fraction.

The "good prognosis" estrogen-receptor-positive and early-stage node-negative cases in both racial groups had similar S-phase fractions, she said. In "bad prognosis" tumors, on the other hand, stage for stage, black women had higher S-phase fractions.