A study presented at the San Antonio Breast Cancer Symposium has reported that obesity is associated with reduced survival for breast cancer patients treated with surgery and chemotherapy, but only among women with hormone receptor positive disease than is not HER2 overexpressing. Obesity has previously been reported to be associated with worse breast cancer outcomes. The study evaluated the effect of obesity (defined as BMI over 30 kg/m2) on outcomes in three Eastern Cooperative Oncology Group trials (E1199, E5188 and E3189). Participants did not have stage IV breast cancer, but had tumors that warranted treatment with Adriamycin chemotherapy (based on tumor size and/or lymph node status). The relationships between body mass index and disease free survival and overall survival were examined, while adjusting for other factors known to influence prognosis, such as tumor size, lymph node status, type of surgery, race, menopausal status, and treatment adherence.

The authors first examined results of the E1199 trial and found weak evidence of inferior disease free survival and overall survival for obese subjects compared with others. However, when the results were analyzed according to breast cancer subtype, obese women with estrogen receptor positive (ER+) and/or progesterone receptor positive/not HER2 overexpressing (PR+/HER2-) disease were found to have 24% higher risk of breast cancer-related death and 42% higher risk of death from any cause than non-obese women. This result was not found for HER2+ or triple negative (ER-/PR-/HER2-) disease. The authors then investigated the relationship between obesity and survival in the other two trials, which included only premenopausal women with ER+, lymph node positive breast cancer (E5188) and both premenopausal and postmenopausal women with ER-/PR-, node positive disease (E3189). These analyses also confirmed a relationship between obesity and poor outcomes only in women with hormone receptor positive disease. The authors conclude that obesity is associated with significantly inferior disease free survival and overall survival in hormone receptor positive operable breast cancer treated with adjuvant chemotherapy. The authors comment that the findings suggest that excess circulating insulin or other factors associated with obesity may predispose hormone receptor positive breast cancer to recurrence.

Please see our article on what ER+/PR+ breast cancer patients and survivors should eat for more information on controllable factors that may influence survival.