Regular moderate exercise improves survival among women with breast cancer, according to numerous studies. Exercise reduces inflammation, decreases circulating estradiol and androgen levels, and induces beneficial changes in insulin levels and insulin-related pathways. Exercise appears to boost immunity and influence the regulation of tumor suppressor genes in ways that have a favorable impact on survival. In addition, aerobic exercise can help decrease tumor hypoxia, a low-oxygen condition under which solid breast tumors can thrive. Now a new study has confirmed previous findings that survival is more likely among women who are physically active after diagnosis. The authors also report a new finding that women who reduce their level of physical activity after diagnosis increase their risk of breast cancer-specific mortality two-fold.
Exercise improves breast cancer prognosis
Women who are physically active after completing treatment for breast cancer are more likely to survive, even those reporting low levels of physical activity prior to diagnosis. The amount of exercise required to improve prognosis is modest — only about half an hour per day of brisk walking. However, higher levels of physical activity are likely to have a greater positive impact on prognosis. On the other hand, there is some evidence that extremely high levels of exercise are not desirable, whether during treatment with chemotherapy or radiotherapy, or after such treatment. Sedentary behavior such as sitting for long periods are not associated with reduced survival among regular exercisers. In addition, regular exercise plus a high quality diet can overcome the negative effects of obesity on survival.
Some observers have suggested that since healthier women are more able to exercise, this factor might account for the observed differences in prognosis between survivors who exercise and those who do not. However, a study that examined this question reported that the associations between exercise and survival were not modified by taking into account other medical conditions, quality of life, or body size. In other words, the study participants benefited from exercise even if they were overweight or were not in good health.
Latest research reports links between exercise and survival
The study referenced at the beginning of this news story was designed to investigate the associations between physical activity and mortality in women diagnosed with breast cancer. To conduct the study, the authors used data from the Norwegian Women and Cancer study (which was open to enrollment from 1991 to 2003), the Cancer Registry of Norway, and the National Register for Causes of Death. The study included 1,327 breast cancer patients who were followed for mortality through year-end 2012. Self-reported physical activity levels were evaluated both before and after diagnosis.
Physical activity levels before diagnosis were not found to be associated with breast cancer-specific mortality or all-cause mortality (i.e., death from any cause, not just breast cancer). However, levels of physical activity after diagnosis were associated with a significant dose-response trend of lower breast cancer-specific and all-cause mortality. These associations were stronger among postmenopausal women (aged 50 to 74) and did not differ according to body mass index. In other words, increasing levels of exercise were linked to decreasing likelihood of death and both heavy and lean women benefited from exercise.
Women who reduced their levels of physical activity after diagnosis were found to have double the likelihood of breast cancer-specific mortality as women who did not reduce their level of physical activity. In fact, mortality was similar among these women as among women who had inactive lifestyles both before and after diagnosis. All-cause mortality was 1.8 times higher among women who reduced their activity levels. The authors comment that their results are very promising for women with breast cancer, and suggest that health care professionals should consider recommending exercise or other physical activity as a part of primary cancer treatment.
Please see our article on exercise for more information.