Lead researcher Dr. Sao Jiralerspong, an assistant professor of medicine at Baylor College of Medicine, and colleagues used data from the Lester and Sue Smith Breast Center at Baylor involving 4,368 patients treated from 1970 to 1995.
For the group as a whole, data revealed that overweight patients had outcomes similar to those for normal-weight patients, but obese patients had an increased risk for shorter time to recurrence, disease-free survival and overall survival, Jiralerspong said. Among patients who received no chemotherapy or endocrine therapy, there was a trend for worse survival outcomes in obese patients compared with normal-weight patients, the study said.
Obese patients who received chemotherapy fared significantly worse compared with normal-weight patients, "with the magnitude of this effect approaching that of the degree of benefit expected from chemotherapy," Jiralerspong said. However, overweight patients who received endocrine therapy, predominantly tamoxifen, fared significantly better compared with normal-weight patients.
"The findings add to the body of evidence indicating that obesity, in general, increases a patient's chance for having a worse prognosis," Jiralerspong said in a statement. "Obesity is a probable risk factor for worse breast cancer outcomes, and ours is the latest study to suggest it has an effect on treatment outcome as well."
The findings were presented at the Cancer Therapy & Research Center-American Association for Cancer Research San Antonio Breast Cancer Symposium.