In this large, population-based study of black women and white
women diagnosed with invasive breast cancer between ages 35 and
64 years, black women had greater risk of mortality than white
women overall. High BMI 5 years before diagnosis was associated
with increased risk of all-cause and breast cancer–specific
mortality among white women, but not among black women. Because
black women generally have a higher prevalence of obesity than
white women at the time of breast cancer diagnosis, several
authors have postulated that obesity could explain some of the
observed racial differences in mortality.21–24 However, our data
do not support this hypothesis. Black women were more likely
than white women to have lower education levels, ER-negative
tumors, nonlocalized tumors, and comorbidities. All of these
factors were associated with increased risk of mortality. After
considering age, education, study site, tumor stage, ER status,
and comorbidities, obesity did not further explain any
differences in mortality risk