High Body Mass Index Was Associated With Human Epidermal Growth Factor Receptor 2-Positivity, Histological Grade and Disease Progression Differently by Age.

Background: Breast cancer is the most commonly occurring cancer among women. The relationship between the obesity paradox and breast cancer is still unclear. The goal of this study is to elucidate the association between high body mass index (BMI) and pathological findings by age. Methods: We collected BMI information pertinent to breast cancer patients from the Gene Expression Omnibus (GEO) database. We use a BMI of 25 as a boundary, and those greater than 25 are defined as high BMI. Besides, we segregated the patients based on age into two age groups: < 55 years, and > 55 years. In this study, R × C Chi-square for trend and binary logistic regression was used to estimate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs). Results: Higher BMI was associated with less breast cancer incidence in females younger than 55 years of age (OR = 0.313, CI: 0.240 - 0.407). High BMI was associated with human epidermal growth factor receptor 2 (HER2) positivity in breast cancer patients of less than 55 years (P < 0.001), but not in the older patients. High BMI was associated with histological grade lower than 2 in the breast cancer patients older than 55 years, but not in younger patients (OR = 0.288, CI: 0.152 - 0.544). Besides, high BMI was associated with worse progression-free survival in younger breast cancer patients, but not in older patients (P < 0.05). Conclusions: Our results described a significant relationship between breast cancer incidence and BMI at different ages and benefit breast cancer patients to implement strategies to control their BMI for reducing the recurrence and distant recurrence.