Other Illnesses Play Role in Difference in Breast Cancer Survival Rates Between Blacks and Whites

Behind the Cancer Headlines®

October 12, 2005

Black breast cancer patients have shorter survival than white breast cancer patients largely because of a higher rate of other disorders, such as diabetes and hypertension, according to a study published in the Journal of the American Medical Association.

Although breast cancer survival has improved over the last 30 years, disparities in breast cancer survival between blacks and whites have not declined and remain sizeable, according to background information in the article. The 5-year U.S. survival rates in 1995-2000 for black and white breast cancer patients were 75 percent and 89 percent, respectively. Although several causes have been identified, such as advanced cancer stage, lack of access to medical care, inferior treatment, and lower socioeconomic status (SES), not all reasons for this disparity are understood.

C. Martin Tammemagi, Ph.D., of Brock University, St. Catharines, Ontario, Canada and colleagues evaluated data from breast cancer patients to evaluate the associations between adverse comorbidities (co-existing illnesses) and racial survival disparity. A group of patients (n = 906) from the Henry Ford Health System (a large comprehensive health system in Detroit) were followed up for a median of 10 years. Patients included 264 black (29.1 percent) women and 642 white (70.9 percent) women diagnosed as having breast cancer between 1985 and 1990. Detailed comorbidity data (268 comorbidities) and study data were abstracted from various medical records, databases and registries.

A total of 159 blacks (61.9 percent) and 317 whites (50.4 percent) died. Overall, 62.4 percent of deaths were attributed to competing causes. Proportionately more blacks than whites died of breast cancer (64 [24.9 percent] vs. 115 [18.3 percent]) and of competing causes (95 [37.0 percent] vs. 202 [32.1 percent]). Compared with whites, blacks had shorter overall survival (34 percent more likely), breast cancer–specific survival (47 percent more likely to have shorter survival), and competing-causes survival (27 percent more likely to have shorter survival). One or more comorbidities were reported in 221 blacks (86 percent) and 407 whites (65.7 percent). A total of 77 adverse comorbidities were associated with reduced survival. Comorbidity count was associated with all-cause and competing-causes survival but was not associated with recurrence/progression or breast cancer–specific survival. Comparisons of unadjusted and comorbidity-adjusted hazard ratios indicated that comorbidity explained 49.1 percent of all-cause and 76.7 percent of competing-causes survival disparity. Diabetes and hypertension were particularly important in explaining disparity.

"Our findings indicate that control of comorbidity may be an important way of improving the survival of black breast cancer patients and reducing racial disparity. That comorbidity explained more than 40 percent of the survival disparity in patients younger than 70 years indicates that effective management of comorbidity has the potential to lead to a substantial increase in person-years of life gained. Control of just 2 comorbidities, diabetes and hypertension, could have a major beneficial impact," the authors conclude.

SOURCE:

Journal of the American Medical Association, October 12, 2005