Newswise — Women who are obese when they are diagnosed with early stage breast cancer are at greater risk of dying of their disease than women of normal weight, according to a new study presented October 6, 2004, at the American Society for Therapeutic Radiology and Oncology's 46th Annual Meeting in Atlanta.
The influence of obesity on breast cancer outcome has been uncertain, especially in early stage breast cancer patients. Previous studies have shown obesity to be a risk factor in the development of breast cancer, but they have reported contradictory results regarding the influence of obesity on survival rates.
In this study, researchers analyzed the data of 2,010 patients from 1978 to 2003 with stage I/II breast cancer, who were treated with breast conserving surgery (lumpectomy), lymph node removal and radiation therapy, with or without chemotherapy. Patients were categorized into three groups according to their weight. Using the body mass index, 452 patients were considered of normal weight, 857 overweight and 701 obese.
Researchers found that the overall five-year survival rates for the patients in the normal and overweight groups were both 92 percent compared to 88 percent for the patients in the obese group. The five-year rates of distant metastasis were 7 percent, 6 percent and 10 percent for the normal weight, overweight and obese weight groups, respectively.
"We have demonstrated a significant association between obesity and adverse breast cancer outcome in patients with early stage breast cancer," said Penny Anderson, M.D., lead author of the study and a radiation oncologist at Fox Chase Cancer Center in Philadelphia. "Despite being diagnosed with breast cancer early, when it is most curable, we found that obese women are more likely to develop metastatic disease and subsequently die of their cancer. Because the prevalence of obesity increases with age, as does the risk for breast cancer, interventions that enhance weight control may have a substantial effect on breast cancer outcome."
ASTRO is the largest radiation oncology society in the world, with more than 7,500 members who specialize in treating patients with radiation therapies. As a leading organization in radiation oncology, biology and physics, the Society is dedicated to the advancement of the practice of radiation oncology by promoting excellence in patient care, providing opportunities for educational and professional development, promoting research and disseminating research results and representing radiation oncology in a rapidly evolving socioeconomic healthcare environment.