Abstract
The effects of obesity on breast cancer prognosis may be subtype-dependent. However, research on premenopausal women with HR + HER2- subtype is insufficient. We included premenopausal women with HR + HER2- early breast cancer who received radical surgery in 42 breast centers nationwide from 2016 to 2021. Patients were classified into four groups according to body mass index (BMI): underweight (UW), normal weight (NW), overweight (OW), obesity (OB). Kaplan-Meier curve was used to compare disease-free survival (DFS) between different BMI groups. Multivariate cox regression analysis was used to identify the effect of obesity on prognosis. Total 5094 patients were included in the analysis. DFS in OB patients was significantly worse than that in patients with NW (p = 0.002). After adjusted for age, tumor size, lymph node involvement, Ki67 index, PR, chemotherapy, radiation therapy and OFS, obesity remains an independent prognostic factor for DFS in premenopausal patients with HR + HER2- breast cancer (p = 0.043). In OW/OB patients who only received selective estrogen receptor modulators (SERMs), DFS was significantly worse than that in UW/NW patients (p = 0.0067). However, OW/OB does not affect DFS in patients who received ovarian function suppression (OFS) (p = 0.865). Furthermore, analysis from Restricted Cubic Splines (RCS) showed that the risk of recurrence continues to increase with increasing BMI in overweight and obese patients. Our study confirmed that obesity stands as an independent prognostic factor for DFS in premenopausal patients with HR + HER2- breast cancer. OFS may reverse the prognosis of premenopausal women with HR + HER2- breast cancer who only receiving SERMs.