Relationship between body mass index (BMI) at diagnosis of ER+ node negative breast cancer (BC) and Oncotype DX recurrence score.

Abstract

582 Background: Inferior stage-adjusted survival for BC among obese (O) women has been reported. This may reflect differences in treatment planned for O women, in treatment received (due to toxicity), or in tumor biology arising in different cellular environments, such as high serum insulin levels, which are associated with a higher risk of recurrence. Methods: We examined whether overweight (BMI 25-30) or obese (BMI >30) women had a higher Oncotype Dx Recurrence Score (RS) after ER+, node negative (NN) or N0i+ BC than normal weight women. Included were all participants at the BC Cancer Agency in a RS clinical utility study in consecutive ER+ NN, N0i+ BC (n=156) at the BC Cancer Agency and in the TAILORx trial (n=56). Sixteen were excluded (n=5 withdrew consent; 1 triple negative; 3 test failed; 2 her2+; 1 neoadjuvant treatment, n=4 height and weight missing). Results: A similar proportion of O patients had low, intermediate, and high RS tumors. Cancers with a high RS were more likely to be grade 3 (55% of grade 3 tumours had high RS, 33% intermediate RS, 12% low RS) and fewer were strongly ER positive (69% of high RS versus 97% of intermediate and low RS). Conclusions: While this data does not support differences in tumor risk arising in O versus non obese environments in ER+, NN BC, examination of a larger data set may be more informative. [Table: see text]