Breast cancer outcomes in a population with high prevalence of obesity

Obesity has been associated with poor prognosis in breast cancer. However, most previous studies examined populations with relatively low proportions of obese patients. Given that forecasts predict obesity rates to exceed 50% by 2030, it is important to examine breast cancer outcomes in populations with higher rates of obesity. We hypothesized that obesity, as measured by body mass index (BMI), is associated with decreased overall survival and disease-free survival in patients with invasive breast cancer in a population with a high prevalence of obesity.

A retrospective review of a prospectively maintained database was conducted on patients treated for invasive breast cancer at an academic medical center between 1997 and 2013. BMI was calculated from each patient's height and weight at the time of diagnosis. Patients were categorized as normal (BMI <25 kg/m(2)), overweight (BMI 25-30 kg/m(2)), or obese (BMI >30 kg/m(2)), as per the definitions established by the World Health Organization. The end points of overall survival and disease-free survival were analyzed.

A total of 523 patients with invasive breast cancer were included for analysis. Based on BMI, 87 (16%) were categorized as normal, 150 (29%) were overweight, and 286 (55%) were obese. The median follow-up was 49 mo. There were 16 deaths (18.4%) in normal patients, 25 (16.7 %) in overweight patients, and 45 (15.7%) in obese patients (P = 0.84). By Kaplan-Meier survival analysis, there were no differences in overall survival (P = 0.49) or in disease-free survival (P = 0.33) among the three groups.

Obesity is not associated with decreased overall or disease-free survival in a patient population with a high prevalence of obesity. These findings suggest that there may be other factors that contribute to the poor prognosis of obese breast cancer patients observed in populations with lower rates of obesity.