Race, anthropometric factors, and stage at diagnosis of breast cancer

A recent study suggested that the greater prevalence of severe obesity amon g African-American women explained almost one third of the observed differe nces between African-American and White women in stage at diagnosis of brea st cancer. The objective of this investigation was to attempt to replicate these findings in a second, larger population and to expand the analyses by including a measure of body fat distribution, the waist:hip ratio. The aut hors used data from a population-based study in North Carolina comprising 7 91 breast cancer cases (302 in African-American women and 489 in White wome n) diagnosed between 1993 and 1996. African-American women were more likely to have later-stage (TNM stage greater than or equal to II) breast cancer (odds ratio (OR) = 2.2; 95% confidence interval (CI): 1.6, 2.9). They also were much more likely to be severely obese (body mass index greater than or equal to 32.3) (OR = 9.7; 95% CI: 6,5, 14.5) and to be in the highest tert ile of waist:hip ratio (OR = 5.7; 95% CI: 3.8, 8.6). In multivariate logist ic regression models, adjustment for waist:hip ratio reduced the odds ratio for later-stage disease in African-American women by 20%; adjustment for b oth waist:hip ratio and severe obesity reduced the odds ratio by 27%, These observations suggest that obesity and body fat distribution, in addition t o socioeconomic and medical care factors, contribute to racial differences in stage at breast cancer diagnosis.