Breast cancer stage, molecular subtype and survival in patients with obesity: a real-world study

Breast cancer (BC) is a leading cause of cancer-related deaths worldwide. Obesity, an established risk factor for BC in postmenopausal women, may also affect prognosis. This study evaluated the impact of obesity on the survival of BC patients treated at a public reference center in Brazil.

A retrospective cohort study was conducted with 7,424 BC patients treated at Hospital da Mulher (São Paulo, Brazil) from January 2011 to June 2021. Patients were categorized into four groups based on body mass index (BMI): underweight, healthy weight, overweight, and obese. Clinical, pathological, staging, and immunohistochemistry data were analyzed. Survival outcomes (overall and progression-free) were assessed using Kaplan-Meier estimates, with comparisons via logistic and Cox regression.

Among the patients, 67.81% were overweight or obese, and 64.82% were postmenopausal (assumed ≥50 years old). A total of 6,992 patients were included in the survival analysis, with 3.79% succumbing to BC. No statistically significant differences in overall or progression-free survival were observed across BMI categories.

While obesity is highly prevalent among Brazilian women with BC, it did not significantly impact survival outcomes in this study. These findings underscore the need for prospective studies to explore potential confounding factors and long-term effects, as well as to inform tailored interventions in similar healthcare settings.