A new study has reported that women who are physically active after completing treatment for breast cancer are more likely to survive than those who are not. Previous studies have reported that physical activity is associated with improved breast cancer survival, but no studies have examined the influence of changes in physical activity after a diagnosis of breast cancer. The study included 2,361 Stage I to Stage III breast cancer survivors who had completed initial treatment (i.e., surgery, radiation and/or chemotherapy) and were enrolled in a study of dietary change. Participants' levels of physical activity were assessed at baseline (i.e., after treatment) and one year later. Physical activity measures (total activity, whether the activity was moderate or vigorous, and adherence to exercise/activity guidelines) were calculated for both time points. The women were followed for a median period of 7.1 years. Any new invasive breast cancer events and death from any cause were recorded.

Women who were most active after completing treatment were found to have a 53% lower risk of death compared to the least active women. Adherence to activity guidelines was found to be associated with a 35% lower mortality risk. On the other hand, neither level of activity after completing treatment nor one-year change in activity were related to local or distant recurrences. The authors conclude that higher post-treatment physical activity was associated with improved survival. However, change in activity over the following year (including, for example, increases in exercise) did not appear to influence recurrence. The data suggest that long-term physical activity levels are important for breast cancer prognosis.

Comments regarding the study

The results of this study can be interpreted to mean that exercise improves survival after breast cancer. However, women who are physically active may have a healthier lifestyle overall, which may contribute to increased survival. Also, some women may be unable to be active because they are unwell or frail, putting them at higher risk of death. The fact that improvements in level of physical activity did not appear to influence the risk of breast cancer recurrence in the study participants indicates that the benefits of exercise may accrue primarily to those who have been engaging in it on a longer-term basis. Apparently, beginning an exercise program after treatment for breast cancer does not produce an immediate survival benefit.

Other studies have also reported that moderate physical activity reduces risk of breast cancer and may improve survival (see studies below). Note that heavy exercise is not recommended during radiation or chemotherapy because it might interfere with the effectiveness of treatment.