Black women with breast cancer do not live as long as white women with breast cancer, largely because of a higher rate of competing illnesses or “comorbidities,” according to a study in this week’s issue of the Journal of the American Medical Association.

In the study, comorbid illness explained roughly half of the overall survival disparity between black and white women and the majority of the competing-causes survival disparity.

“Diabetes and hypertension are the two most important comorbidities accounting for survival disparities” among black and white women, study chief Dr. C. Martin Tammemagi from Brock University, St. Catharines, Ontario told.

Effective control of these and other comorbid conditions in black breast cancer patients “should help improve their life expectancy and reduce survival disparities,” the researcher said.

Overall, breast cancer survival rates have improved in the last three decades. However, disparities in breast cancer survival between blacks and whites have not declined and remain sizable. Advanced cancer stage, lack of access to medical care, inferior treatment, and lower socioeconomic status likely explain some, but not all, of this disparity.

Tammemagi’s team evaluated the role of comorbid illness and racial survival disparity in a cohort of 906 breast cancer patients who were followed for a median of 10 years. Two hundred sixty-four of the women were black (29 percent) and 642 were white (71 percent).

A total of 159 black women (62 percent) and 317 white women (50 percent) died during follow-up.

Black breast cancer patients had more cancer recurrence and more progression of their cancer and worse overall survival and breast-cancer specific survival.

According to the team, most black and white breast cancer patients died of causes unrelated to their cancer. Thirty-seven percent of black women died of an illness other than breast cancer while 25 percent died of breast cancer. The corresponding figures for white women were 32 percent and 18 percent.

When the team evaluated the impact of 268 different comorbidities, they found that 77 were associated with reduced survival. At least one of these comorbid illnesses was present in 86 percent of blacks compared with 66 percent of whites.

Diabetes and hypertension were particularly important in explaining survival disparities between black and white women.

The finding in this study that comorbid illnesses explained more than 40 percent of the survival disparity in patients younger than 70 years indicates that effective management of these illnesses has the potential to lead to a substantial increase in years of life gained, the team contends. Controlling Diabetes and hypertension alone “could have a major beneficial impact,” they add.

SOURCE: Journal of the American Medical Association October 12, 2005.