Abstract P6-05-04: Relationship between obesity and breast tumor pathology in a contemporary set of patients

Abstract

Abstract Background: Obesity is a risk factor for breast cancer in postmenopausal women, and is associated with decreased survival regardless of menopausal status. This outcome disparity has been attributed to clinical factors such as delayed diagnosis, inadequate dosing with chemotherapeutic agents, and co-morbid conditions. Here, we evaluated the association between pathological characteristics and BMI in a cohort of patients enrolled in the Clinical Breast Care Project (CBCP) 2001-2013. Methods: All female patients with invasive breast cancer who had height and weight recorded at the time of diagnosis were identified from the CBCP database. BMI was calculated and patients categorized as normal/lean (<24.9 kg/m2), overweight (25-29.9 kg/m2), or obese (>30.0 kg/m2). Chi-square univariate analysis was performed to determine statistical significance followed by multivariate logistic regression. Statistical significance was defined as p <0.05. Survival analysis was done using Cox proportional hazard regression models. Results: Of the 1,705 patients, 32.4% were normal/lean, 31.6% were overweight and 36.0% were obese. Univariate analysis revealed that obese women were significantly more likely to be older at age at diagnosis, African American, menopausal and treated at Joyce Murtha Breast Care Center, a rural civilian hospital in western-central PA. These factors were thus include in multivariate analysis which showed that obese patients were at an increased risk relative to normal/lean patients of having a higher tumor stage (OR = 1.32, 95% CI [1.043-1.681], p = 0.021), size (OR = 1.42, 95% CI [1.091-1.857], p = 0.009), and grade (OR = 1.37, 95% CI [1.085-1.718], p = 0.008) but at decreased risk of PR- tumors (OR=0.57, 95% CI [0.394-0.837], p = 0.004). Overweight patients did not differ significantly from either normal weight or obese patients. Neither breast cancer-specific nor overall survival differed significantly between groups. Discussion: Higher tumor stage and size may reflect delayed detection in obese women. In contrast, tumor grade and PR status likely reflect underlying biological differences driven by increased adiposity in the breasts of obese women. Despite these differences in pathology, survival did not differ by BMI status, suggesting that factors such as suboptimal dosing may not be relevant in current patient care. Citation Format: Ellsworth RE, Lovejoy L, Costantino N, Sheiver CD. Relationship between obesity and breast tumor pathology in a contemporary set of patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-05-04.