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The higher mortality rate among black breast cancer patients may be partially explained by a higher frequency of other serious medical conditions among black women, according to a study published in the Journal of the American Medical Association.

As breast cancer mortality has decreased, racial differences in survival have persisted. During 1995-2000, the five-year breast cancer survival rate was 75% for black women and 89% for white women. The reasons for this difference are not fully understood, although factors such as more advanced cancers among black women and differences in access to care appear to play a role.

The presence of other health problems in addition to breast cancer is known to influence survival among breast cancer patients. Researchers therefore raised the question of whether the frequency of these other health problems could explain some of the difference in breast cancer survival between black women and white women.

To evaluate the impact of other health problems on death from breast cancer, death from causes other than breast cancer and death from all causes combined, researchers evaluated 906 women enrolled in a managed care organization in Michigan.

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The women (264 black and 642 white) had been diagnosed with breast cancer between 1985 and 1990. They were followed for a median of 10 years after diagnosis in order to assess survival. Information about other health problems was collected from the patients’ medical records. These other conditions included infectious disease, cardiovascular disease, respiratory disease, cancers other than breast cancer, diabetes, anemia, mental disorders, nervous system disorders (such as Parkinson disease, epilepsy or glaucoma), digestive diseases, kidney problems, osteoporosis, and injury.

During the roughly 10 years of follow-up, researchers recorded the following results:

  • 25% of the black breast cancer patients died of breast cancer and 37% died of other causes.
  • White women experienced fewer breast cancer deaths and fewer other deaths: 18% of white breast cancer patients died of breast cancer and 32% died of other causes.
  • Black women were also more likely to have at least one serious medical problem other than breast cancer: 86% of black women had at least one other medical condition, compared to 66% of white women. These other health problems accounted for roughly half of the racial difference in all-cause mortality, and three quarters of the racial difference in mortality from causes other than breast cancer.
  • Diabetes and hypertension were the conditions that explained the greatest amount of the racial disparity in mortality.

This study suggests that effectively preventing or controlling the health problems that are more common in black women, particularly diabetes and hypertension, could have a large impact on the survival of black women with breast cancer, and could reduce the difference in breast cancer survival between black women and white women.

Reference: Tammemagi CM, Nerenz D, Neslund-Dudas C et al. Comorbidity and survival disparities among black and white patients with breast cancer patients. JAMA. 2005;294:1765-1772.