Overweight and obese women face greater risks of breast cancer recurrence or related death than women at normal weight, even after chemotherapy dose adjustment for weight, according to a study presented March 23 at the 8th European Breast Cancer Conference (EBCC-8) in Vienna. Although the link between obesity and the development of breast cancer is well known, there has been less research to date looking at its effect on cancer recurrence and survival.
Jennifer Ligibel, MD, a medical oncologist at Dana-Farber Cancer Institute in Boston, and colleagues studied data from 1,909 patients who were enrolled into the CALGB 9741 study between 1997 and 1999. The study was set up to investigate different dosing schedules for adjuvant chemotherapy in patients with node-positive breast cancer.
After extracting height and weight data from patient records, Ligibel and colleagues evaluated the relationship between body mass index (BMI) with relapse-free survival (RFS) and overall survival (OS).
Among the women in the study, 1.2 percent of the patients were underweight, 32.6 percent were normal weight, 32.9 percent were overweight and 33.3 were obese.
"Several other studies have shown that being overweight or obese at the time that a woman is diagnosed with breast cancer is linked to a higher risk of recurrence. However, questions have been raised in the past whether obese women were receiving relatively lower doses of chemotherapy due to their weight. Our study mandated that each patient received a chemotherapy dose adjusted to her weight, so these results suggest that treatment factors are not responsible for the differences in recurrence rates seen in heavier women," Ligibel said in a statement.
"We found that BMI was related to both RFS and OS; for example, the ten-year RFS of a patient who was overweight was 70 percent; compared with 65 percent for one who was obese." Adjusted analyses showed each unit of increased BMI was associated with a 1.5-2 percent increase in the risk of recurrence and mortality, according to the researchers.
Ligibel and colleagues intend to follow up their work by learning more about how weight-related factors could influence breast cancer outcomes.