A new study has reported that exercise improves outcomes for early stage breast cancer patients. The study was designed to investigate the association between exercise after breast cancer diagnosis and survival, taking into account factors that restrict exercise participation. It has been reported that exercise following a diagnosis of breast cancer is inversely associated with mortality. However, whether such associations indicate causality is controversial (it has been argued that healthier women are more able to exercise and that this largely accounts for the observed differences in prognosis). The study included 4,826 women in the Shanghai Cancer Registry with stage I-III breast cancer. The women, who were identified within six months of diagnosis, were recruited into the study between 2002 and 2006. The women were followed for a median of 4.3 years. Level of exercise was assessed and metabolic equivalent (a measure of exercise intensity) scores were recorded approximately six, 18, and 36 months after diagnosis. Personal interviews were used to obtain information on medical history, cancer diagnosis, treatments, quality of life, height, weight, and lifestyle factors at baseline (six months after diagnosis). Medical charts were reviewed to verify breast cancer-related information.

A total of 436 deaths and 450 new breast cancer events (recurrences and breast cancer-related deaths) occurred among study participants during the follow-up period. Regular exercise during the first 36 months after diagnosis was found to be associated with 30% lower risk of death from any cause and 40% lower risk of new breast cancer events than little or no exercise, after adjusting for quality of life, clinical prognostic factors, and other relevant variables. Higher levels of exercise duration and intensity resulted in lower overall risk of death and breast cancer events, demonstrating a dose-response relationship between exercise and breast cancer prognosis. The associations between exercise and mortality were not changed by taking into account menopausal status, other medical conditions, quality of life, or body size at baseline. In other words, participants generally benefited from exercise regardless of whether they were overweight or were not in good health. The authors conclude that exercise after breast cancer diagnosis might improve overall survival and disease-free survival.