WASHINGTON — Aggressive breast tumors, known as “triple negatives,” are significantly more common among black women—especially younger women—than in white women, reported Mary Jo B. Lund, Ph.D., at the annual meeting of the American Association for Cancer Research.
Tumors that test negative for three biomarkers—estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2)—are not only more aggressive than are other subtypes of breast cancer, but they can't be treated effectively with tamoxifen or trastuzumab, said Dr. Lund of Emory University in Atlanta.
Dr. Lund and her colleagues evaluated the potential racial differences in the incidence of triple-negative tumors in a group of 117 black women and 362 white women aged 20–54 years. The women had been diagnosed with breast cancer between 1990 and 1992 and were enrolled in a population-based, case-control breast cancer study in the Atlanta area.
The overall incidence of triple-negative tumors was 29.5%, but the tumors were significantly more common among black women, compared with white women (47% vs. 22%).
The incidence of triple-negative tumors decreased with age among white women, but was consistent across age groups among black women. “Essentially, across all age groups, black women were twice as likely to have these triple-negative tumors,” Dr. Lund noted.
Younger black women, aged 20–34 years, appeared to be at particular risk; more than 50% of the tumors in this age group were triple negative. In addition, the percentage of triple-negative tumors increased with increasing severity among both races, but the incidence of grade 3 tumors remained higher among black women, compared with the incidence in white women (81% vs. 66%).
Crucial decisions about breast cancer treatment are based on the presence or status of ER, PR, and HER2 tumors, said Dr. Lund. “Almost 30% of all women and 50% of black women have tumors for which there is no targeted therapy.”
Future research on triple-negative tumors should focus on the risk factors, the reasons for increased risk among black women, and the possible roles of genetics and other biomarkers, she added.