Tumor characteristics in obese women with breast cancer.

Abstract

179 Background: Obesity is an established risk factor for postmenopausal breast cancer. Though women with high BMI tend to develop less aggressive molecular subtypes, previous studies have shown that they still have a higher risk of recurrence and worse prognosis. The biological mechanisms for this difference in outcome have yet to be identified. The purpose of this study is to determine the correlation between obesity and tumor characteristics, including Ki67, and Oncotype DX scores in both pre- and post-menopausal women. Methods: The Breast Cancer Database of NYU Langone Medical Center was queried for patients who were newly diagnosed with invasive breast cancer. We looked at the following variables: menopausal status, body mass index (BMI), histology, stage, ER/PR/Her2-neu status, Ki67, and Oncotype DX scores. Obesity was defined as having a BMI (kg/m2) ≥30. We looked at Ki67 as a continuous variable. Oncotype scores were categorized as low (<18), intermediate (18-30), and high (>31). Statistical analyses were performed using Spearman Correlation Coefficients. Results: Out of a total of 648 patients with a median age of 59 years, 153 (24%) women had a BMI≥30. The majority of the obese women had stage I and II (88%) cancers that were ER positive (84%), PR positive (74%), Her2-neu negative (86%), with mean Ki67 of 22%, and low to intermediate Oncotype DX scores (85%). However, when compared with women of BMI <30, there was no correlation between BMI and tumor characteristics, even when stratified by menopausal status. Conclusions: In our cohort, obesity was not correlated with tumor stage, histology, Ki67 and Oncotype DX scores, even after adjusting for menopausal status. There are other factors that may explain the higher risk of recurrence and worse prognosis of breast cancer in obese women, such as insulin resistance, and obesity-related inflammatory cytokines that are independent of breast cancer subtypes and genomics. Treatment-related factors, such as non-compliance and inadequate dosing of chemotherapeutic agents, may also play a role in the worse outcome seen in this population. Further studies are necessary to identify measurable molecular characteristics of breast cancer in obese women that would allow us to predict more aggressive disease.