Despite higher rates of diabetes (DM), hypertension (HTN), and hyperlipidemia (HLD) with increasing body mass index (BMI), a diagnosis of obesity was not associated with worse overall survival (OS) in women with breast cancer but being overweight was, suggesting the need for a more nuanced understanding of body composition, obesity-associated conditions, and their respective potential impact on breast cancer outcomes.

Women 18 years and older diagnosed with stage 0-IV breast cancer at an academic institution with known BMI at diagnosis were identified. χ2 and ANOVA tests were used to compare intergroup differences. BMI was categorized as normal, overweight, class 1 obesity, and class 2/3 obesity. Unadjusted OS by BMI class was estimated with the Kaplan-Meier method. Of patients included: 296 were overweight, 227 had class 1 obesity, and 207 had class 2/3 obesity. Non-Hispanic (NH) black women were overrepresented among obese patients, making up 25% of all patients but 37.5% of obese patients. Rates of DM, HTN, and HLD increased with increasing BMI. Unadjusted OS differed significantly by BMI class, with overweight women having the worst 5-year OS. After adjustment, BMI continued to be associated with OS, with overweight women having significantly worse OS vs normal-weight women, but there was no significant association between obesity and OS.

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The effect of body mass index on survival in patients with breast cancer and obesity-associated conditions.