The prognostic impact of body mass index in breast cancer according to tumor subtype.

Purpose: Several studies demonstrated that obesity and underweight were negatively associated with outcomes of breast cancer. However, the results are still controversial, and the impact of body mass index (BMI) on distant metastasis-free survival (MFS), which might directly affect mortality, was less well evaluated. Our study aimed to verify the prognostic effect of BMI in breast cancer.

Methods: A retrospective analysis of 504 patients with stage I-III breast cancer who underwent surgery from January 2005 to December 2013 was performed. The patients were divided into three groups according to preoperative BMI: underweight <18.5 kg/m2, normal weight 18.5-24.9 kg/m2, and overweight ≥25 kg/m2. The association between body weight status and breast cancer recurrence was analyzed. Subgroup analysis by tumor subtype according to receptor status was also performed.

Results: The median follow-up period was 88 months. For disease recurrence, histologic grade and human epidermal growth factor receptor 2 (HER2)-positivity were independent prognostic factors in multivariate analysis. Stage, histologic grade, HER2-positivity, and BMI status were independent prognostic factors for distant metastasis. In survival analysis, overweight and underweight were significant predisposing factors for MFS, but not for disease-free survival (DFS). In the estrogen receptor (ER)-positive group, overweight and underweight patients had significantly worse DFS and MFS than normal weight patients. In the ER-negative or HER2-positive group, BMI status had no significant association with DFS and MFS.

Conclusion: The prognostic role of BMI on the survival outcomes of patients with breast cancer was different by tumor subtype. In ER-positive patients, overweight and underweight statuses had a negative prognostic effect on DFS and MFS, respectively.