The HRs for RFS, OS, and BCSS for overweight were 1.18, 1.20, and 1.21, respectively, in a multivariate model adjusted for BMI, diabetes, medical comorbidities, patient- and tumor-related factors, and adjuvant therapy relative to the normal weight. The obese had HRs of 1.13, 1.24, and 1.23 for RFS, OS, and BCSS, respectively. According to subset analyses, these differences were significant for the ER-positive group but not for the ER-negative or HER2-positive groups. Compared to nondiabetics, the HRs for RFS, OS, and BCSS for diabetes were 1.21, 1.39, and 1.04, respectively. This evidence concerns the gene ERBB2 and diabetes mellitus.