Obesity is a negative risk factor for survival in white women with invasive breast cancer, but not in their black counterparts

These findings suggest that differences in the distribution of obesity among black women and white women diagnosed with breast cancer are unlikely to account for the poorer survival of black women. Although both black and white women have benefited from treatment advances for breast cancer, black women continue to have a significantly lower 5-year survival rate, and are more likely to be diagnosed with an advanced stage of the disease. To determine whether the higher rate of obesity in black than white women may contribute to the discrepancy in survival, data for 1604 black and 2934 white women who were 35-64 years old when diagnosed with invasive breast cancer between 1994 and 1998 was examined. Over an average of 8.6 years of follow-up, 1053 of the patients died, with 412 black and 416 white women dying from breast cancer. Analysis confirmed that black women were significantly more likely to die than white Women, with a relative risk (RR) of 1.33, after adjusting for variables including age at diagnosis, education, tumor stage, estrogen receptor status, comorbidity, and race. Obese women, defined as having a body mass index (BMI) of 30 kg/m2 or above, had significantly higher all-cause and breast cancer-specific mortality than women with a healthy BMI of 20.0-24.9 kg/m2, at a RR of 1.23 and 1.20, respectively. When stratified by race, the researchers found that BMI was a significant influence on all-cause and breast cancer-specific mortality in white women (RR=1.54 and 1.46, respectively). However, BMI did not significantly alter all-cause or breast cancer-specific mortality in black patients. It is not clear why obesity-associated mortality risk patterns differ between black women and white women with breast cancer. Normal-weight black women had a greater risk for all-cause mortality than normal-weight white women, but the same was not true for obese black women versus obese white women. This finding agrees with research indicating that BMI has a greater impact on cardiovascular disease on white than black women.