With nine papers published in the last two years, Dr. Melinda Irwin, Associate Professor of Epidemiology and Public Health, certainly keeps herself busy. Specializing in energy balance and cancer prevention and prognosis, Irwin has recently turned her attention to the issue of whether exercise after a breast cancer diagnosis affects prognosis.
“How lifestyle may improve survival after diagnosis is not often studied. Usually, studies focus on the prevention of cancers,” Irwin explained. “However, recently, it was discovered that being overweight and physically inactive increases the risk of a poor prognosis, as well as the likelihood of cancer. After that, more groups have become interested in exploring the effects of physical activity on cancer prognosis.”
In the Yale Exercise and Survivorship Study, Irwin and colleagues recruited 75 postmenopausal breast cancer survivors. Half were randomly selected to participate in an exercise program requiring 150 minutes of moderate-intensity aerobic exercise, such as brisk walking. The other half, serving as the control, maintained their normal lifestyle, which included fewer than 20 minutes of aerobic activity per week. At the beginning of the study and after six months, blood samples were taken to measure the biological markers of prognosis.
Specifically, levels of insulin and insulin-like growth factor 1 (IGF-1), which may be associated with increased breast cancer risk and death, were increased in the usual care groups and lowered in the exercise intervention groups. Thus, decreases in insulin and IGF-1, high levels of which are linked to obesity, may mediate the association between exercise and improved survival post-diagnosis observed earlier. Moreover, one of these studies found that two to three hours of moderate exercise per week resulted in a 40% to 67% reduced risk of death.
In light of these findings, Irwin hopes that one day physicians will introduce exercise programs into the standard breast cancer treatment. With the American Cancer Society and the American College of Sports Medicine, she has already helped to develop a certification for physical therapists, nurses, and trainers that will allow them to counsel and work with cancer patients.
“With the advent of this program, hopefully more insurance companies will reimburse the costs, and physicians will be more likely to recommend it,” Irwin added. “Free access to facilities and trainers is the key to eliminating a large barrier to the recommended levels of exercise.”
Over 75% of Americans exercise less than the recommended 2.5 hours per week. Furthermore, women often gain weight during cancer treatment. Thus, it is even more important for breast cancer patients to maintain high levels of physical activity. However, these patients are likely less inclined than healthy individuals to exercise the recommended amount without the benefit of a trainer.
This summer, Irwin is beginning another study involving exercise and survivorship in women with ovarian cancer. She will also be submitting a grant for a larger study with fifteen sites across the nation that will recruit 2,000 women who have been diagnosed with breast cancer within the year. These women will participate in a five-year long weight loss program, after which Irwin hypothesized about a 10% weight loss and better survival rate compared to control groups. This second study should begin next year.
When asked for advice, Irwin remarked, “People tend to think of cancer as due to a genetic predisposition or family history. But in fact, about 90% of cancers arise due to one’s lifestyles and environment. Thus, it’s especially important for everyone to maintain a healthy lifestyle, which includes daily exercise.”