Higher Body Mass Index Affects Breast Cancer Outcomes
A retrospective study describing the relationship between the body mass index (BMI—whether a person is overweight or not) and the outcome of advanced breast cancer was published in the March 15, 2008, issue of Clinical Cancer Research. This study showed that a those with higher BMI are more likely to be diagnosed with an aggressive form of cancer and have a negative outcome than patients with normal weight.
The study was performed at the University of Texas M.D. Anderson Cancer Center. At this center, all patients with the diagnosis of locally advanced breast cancer (LABC) receive uniform treatments and follow-up procedures, so it is an ideal place to perform a retrospective study. The study demonstrates the relationship between two factors, body mass index and treatment outcome without the obvious confounding variables such as different treatment regiments. LABC can be subdivided into non-metastatic inflammatory (IBC) and non-inflammatory locally advanced breast cancers (non-IBC LABC). The authors were interested in comparing the two subgroups of LABC, IBC and non-IBC LABC, in addition to examining BMI and LABC. All studied patients had stage III LABC.
The study used data from 606 patients. Of these, 495 (82%) patients had non-IBC LABC and 111 (18%) patients had IBC. When the patients were categorized by BMI, 208 (34%) patients were either normal or underweight, and 398 (66%) patients were either overweight (32%) or obese (34%). Overweight and obese patients also had a greater degree of seriousness of the disease, resulting from tumors of higher T stage, higher nodal involvement, and higher grade compared with patients with normal weight. In addition, obese patients had a higher incidence of IBC, the more aggressive form of the disease, than either the overweight or normal/underweight patients.
The overall survival and recurrence-free survival were significantly worse for obese and overweight patients compared with normal/underweight. When IBC and non-IBC LABC were compared, the rates for five-year overall survival and recurrence-free survival for IBC patients were worse compared to non-IBC patients suggesting that prognosis for IBC is worse for non-IBC patient regardless of BMI. Obese or overweight patients had worse overall survival and recurrence-free survival rates within the two subgroups. Therefore, the obese and overweight patients suffering from IBC had the worst prognosis.
Previous studies have shown that obesity can be linked with an increased risk of developing breast cancer. However, this present retrospective study also suggests that higher BMI is correlated with lower overall survival and that the possibility of using BMI as a prognostic tool exists. As the authors of the paper stated, one of the limitations of the study is the lack of data on dietary habits of these 606 patients, given a recent study that suggests correlation between low dietary fat intake and reduced risk of disease recurrence. Despite the limitations, the value of the current study is that it illustrates the importance of a more multidisciplinary approach to the treatment of breast cancer including dietary intervention.
Dawood, S., et al, Prognostic Value of Body Mass Index in Locally Advanced Breast Cancer Clincal Cancer Research 2008:14(6) March 15, 2008.