Impact of Body Mass Index on Local Recurrence according to Intrinsic Subtype Approximation in Korean Women with Early Stage Invasive Breast Cancer Receiving Contemporary Treatments

Purpose: We investigated the prognostic impact of body mass index (BMI) on local recurrence (LR) according to intrinsic subtype in Korean women with early stage, invasive breast cancer. Materials and methods: We included 907 patients with pathological stage T1-2 and N0-1 breast cancer who underwent curative surgery between 2007 and 2012. Systemic treatments were administered in 876 patients (96.6%). In total, 701 patients (77.3%) received radiotherapy. Intrinsic subtypes were determined using immunohistochemical staining results. Results: During the median follow-up period of 72 months, LR as the first failure occurred in 29 patients, including 24 patients with isolated LR. The 5-year cumulative incidence rate of LR was 3.2% among all patients. In the luminal A subtype, a BMI of <18.5 kg/m(2) was an independent risk factor for LR, as determined by a competing-risk regression model (relative risk, 3.33; p = 0.041). Severely obese patients (BMI >30 kg/m(2)) with the triple negative subtype had an increased risk of LR (relative risk, 3.81; p = 0.048). Conclusion: The present study identified traditionally underestimated risk groups for LR. BMI may diversely influence the rate of LR across intrinsic subtypes in Korean patients with breast cancer.