Women who are overweight when they are diagnosed with breast cancer, are at higher risk of dying from the disease or of the cancer returning than leaner women, according to a new study.
The findings 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.
Dr Jennifer Ligibel, a medical oncologist at the Dana-Farber Cancer Institute, in Boston, U.S., and colleagues, looked at data from 1,909 patients, who were enrolled into a study between 1997 and 1999.
The study was set up to investigate different dosing schedules for chemotherapy in patients where cancer cells were found in the lymph nodes. 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 with relapse-free survival and overall survival.
“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,” said Dr Ligibel, who discussed the findings at the 8th European Breast Cancer Conference.
“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.”
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.
Dr Ligibel said with obese rates on the increase it was a matter of urgency that the relationship between obesity and cancer was properly understood.
The researchers intend to undertake further research in this area.
Professor David Cameron, from the University of Edinburgh, said: “There are a lot of health reasons why overweight women should try and get back to a normal weight, but this is not always easy, and as the authors acknowledge, we don’t yet know that losing weight after a breast cancer diagnosis will make a difference.”