Abstract / Summary
Purpose: To examine associations of body mass index (BMI) with sociodemographic, clinical, treatment-related, psychosocial, and patient-reported outcomes among women with non-metastatic estrogen receptor-positive (ER+) breast cancer receiving adjuvant endocrine therapy.
Methods: This multicenter cross-sectional study included 557 women treated at 11 Brazilian public and private institutions from June 2021 to March 2024. Participants were classified as having normal weight, overweight, or obesity. Health-related quality of life was assessed using the EORTC QLQ-C30 and QLQ-BR23. Characteristics were compared across BMI categories using chi-square or Fisher's exact test and Kruskal-Wallis test. Multinomial logistic regression examined factors associated with BMI category, using normal weight as the reference.
Results: Of 557 participants, 172 had normal weight, 234 were overweight, and 151 had obesity. Education, comorbidities, hospital type, cancer stage, endocrine therapy, axillary dissection, prior chemotherapy, and radiotherapy differed across BMI categories. Participants with obesity had poorer physical functioning and greater pain. In the final model (n = 554), axillary dissection (OR = 2.51; 95% CI = 1.37-4.59) and continuous medication use (OR = 2.92; 95% CI = 1.78-4.79) were associated with obesity versus normal weight. Tamoxifen was inversely associated with overweight (OR = 0.58; 95% CI = 0.36-0.91), whereas low treatment adherence (OR = 1.54; 95% CI = 1.01-2.35) and continuous medication use (OR = 1.68; 95% CI = 1.10-2.58) were positively associated.
Conclusion: Overweight and obesity were common and associated with sociodemographic, clinical, treatment-related, and selected quality-of-life characteristics. These findings support integrated survivorship care addressing weight-related health, comorbidities, functional limitations, and symptom burden. Longitudinal studies are needed to clarify temporal relationships.