Aggressive estrogen-receptor-positive breast cancer arising in patients with elevated body mass index.

BACKGROUND: Obese women with estrogen receptor (ER)-positive breast cancer may experience worse disease-free and overall survival. We hypothesize that this observation is due to intrinsically aggressive disease and that obesity will be associated with higher histologic grade and Ki67.
METHODS: A sequential cohort of women with breast cancer diagnosed over 2 years was assembled from institutional tumor registries. Patient and tumor characteristics were abstracted from medical records; those with non-invasive tumors, or lacking body mass index (BMI), Ki67 or histologic grade data, were excluded. Univariate and multivariate analysis was performed to investigate the relationship between markers of aggressive disease (grade and Ki67) and multiple variables associated with obesity. A subgroup analysis was performed to investigate further whether ER and menopausal status influenced associations between BMI and aggressive phenotypes.
RESULTS: Of the 1007 patients initially identified, 668 (68 %) met the eligibility criteria. In univariate analysis, histologic grade and Ki67 were strongly associated with increased BMI, younger age, and African-American race, but less so with diabetes, hypertension, and hyperlipidemia. Multivariate analysis confirmed that higher histologic grade was associated with increased BMI (p = 0.02), and that increased Ki67 was associated with younger age (p = 0.0003) and African-American race (p = 0.002). Additional analysis found that the association between increased BMI and higher-grade tumors was particularly significant in premenopausal women with ER-positive disease.
CONCLUSION: This study concludes that increased BMI is associated with aggressive-phenotype breast cancer and may be particularly relevant to ER-positive breast cancer developing in premenopausal African-American women.