Does obesity have an effect on outcomes in triple-negative breast cancer?

Among patients with breast cancer, obesity has been associated with an increased likelihood of having triple-negative breast cancer (TNBC). This association has been thought to be due to the antiapoptotic effects of obesity-related proteins. However, the effect of obesity on the outcomes in patients with TNBC remains unclear. We hypothesized that obesity would be associated with decreased overall survival and disease-free survival in these patients.

A retrospective review of a prospectively maintained database was conducted of patients treated for breast cancer at an academic medical center from March 1998 to September 2011. The body mass index (BMI) of patients with TNBC was calculated at diagnosis. The patients were categorized as normal (BMI < 25 kg/m(2)), overweight (BMI 25-30 kg/m(2)), or obese (BMI > 30 kg/m(2)). The endpoints of overall survival and disease-free survival were analyzed.

A total of 183 patients with TNBC were included for analysis. Of the 183 patients, 24 (13.1%) were normal (BMI < 25 kg/m(2)), 42 (23.1%) were overweight (BMI 25-30 kg/m(2)), and 117 (63.7%) were obese (BMI > 30 kg/m(2)). The median follow-up period was 42.5 months. Of the 183 patients, 2 (9.1%) died in the normal group, 10 (23.1%) died in the overweight group, and 25 (21.4%) died in the obese group (P = 0.28). The patients who were overweight or obese had larger tumors (P = 0.02), a higher T stage (P = 0.001), and higher tumor grade (P = 0.01) than the normal BMI patients. By Kaplan-Meier analysis, normal patients had higher overall survival than the overweight or obese patients, but this difference was not statistically significant (P = 0.29). Disease-free survival was also not significantly different (P = 0.91).

Despite an increased frequency of larger tumors, higher T stage, and higher tumor grade, obesity was not associated with decreased overall or disease-free survival in patients with TNBC.