It is well-accepted that obesity increases a woman's risk for breast cancer; research now shows that obesity increases negative outcomes once breast cancer occurs. Compared with women breast cancer patients of normal weight, obese women with breast cancer are more likely to have their cancer spread and are more likely to die from their cancer, according to a study by the Fox Chase Cancer Center in Philadelphia. These findings were based on the study of 2010 women with early-stage breast cancer who underwent a lumpectomy, removal of lymph nodes, and radiation therapy with or without chemotherapy. The subjects were divided into normal weight, overweight, and obese groups; women in the obese groups were more likely to be older and postmenopausal, compared with the other groups. The size of the tumor and the number of lymph nodes involved did not differ, yet the 5-year survival rate was 88% for the obese group and 92% for the other groups. Lead author Penny R. Anderson, MD, who presented the study's findings at the annual meeting of the American Society for Therapeutic Radiology and Oncology, said it is still not clear why there is a difference in mortality rates, but it is suspected that the difference may involve estrogen levels and circulating metabolism.