Women who are overweight or obese when they are diagnosed with breast cancer are at higher risk of cancer recurrence or related death than are leaner women, according to a new study presented to the 8th European Breast Cancer Conference (EBCC-8) in Vienna, Austria. This finding held true even though the study mandated that chemotherapy dosage be adjusted for body weight, and adds further to the evidence that lifestyle factors can influence cancer prognosis, a researcher told the conference.

Dr. Jennifer Ligibel, a medical oncologist at the Dana-Farber Cancer Institute in Boston and an Associate Professor at Harvard Medical School, and colleagues, studied data from 1909 patients who were enrolled into a study called CALGB 9741 between 1997 and 1999. The study was set up to investigate different dosing schedules for adjuvant chemotherapy in patients where cancer cells were found in the lymph nodes (node-positive cancer). The presence of such cells in the lymph nodes means that there is a higher chance of cancer returning after surgery.

After extracting height and weight data from the patient records, they went on to evaluate the relationship between body mass index (BMI) with relapse-free survival (RFS) and overall survival (OS). 1.2% of the patients were underweight, 32.6% normal weight, 32.9% overweight, and 33.3% obese. 49% of patients were menopausal, 65% had estrogen-receptor positive cancers, where the presence of estrogen encourages the tumor to grow, and 70% received the estrogen-receptor blocking treatment, tamoxifen.