More than 10 million Americans are cancer survivors. Most are anxious to do anything they can to reduce the risk of a recurrence. But what can be done?
While research abounds on how diet and lifestyle habits affect the initial appearance of cancer, far fewer studies have looked at how to stay healthy and prevent cancer’s return following treatment.
Preventing Cancer From the Start. It’s well accepted that diet and physical activity influence your risk of developing cancer. According to the American Institute for Cancer Research, eating a plant-based diet plays a pivotal role in preventing tumor growth and in slowing its progression. Studies also have found that people who exercise have a lower risk of developing certain kinds of cancer, such as cancers of the breast and colon.
Overweight and obesity increase the risk of some types of cancer. Because regular activity can help with weight management, it logically follows that it plays a role in preventing cancer too.
Preventing Cancer From Coming Back. Studies have only recently begun to look at the effect of diet and exercise on the recurrence of cancer. Researchers have found that eating a nutrient-loaded, plant- based diet after cancer diagnosis and treatment may lessen the likelihood of recur rence or of developing a second cancer.
Likewise, leading an active lifestyle is strongly linked not only to a lower likelihood of getting cancer, but preliminary research suggests that exercise may actually reduce the risk of some cancers recurring, unrelated to its effect on weight (see ?Exercise to Keep Cancer at Bay,? above right).
According to colon cancer researcher Jeffrey Meyerhardt, M.D., M.P.H., of Harvard Medical School, because a sedentary lifestyle is most strongly tied to an increased risk of developing breast and colon cancers, those two cancers are now the focus of much of the research on exercise and cancer recurrence. But researchers are optimistic that future studies will expand the list of cancers for which physical activity might decrease the likelihood of recurrence.
Here’s what we know so far about how activity affects these two cancers.
Exercise and Breast Cancer. Two studies have followed breast cancer survivors, many of whom become sedentary during treatment and never resume their pre-diagnosis activity levels. The Harvard Nurses? Health Study, which included almost 3,000 women with cancer, concluded that regular exercise after a breast cancer diagnosis may ultimately reduce the risk of death from the disease, particularly in women with hormone-sensitive tumors (which grow in response to higher hormone levels).
?We know from past research that active women have lower sex hormone levels than inactive women, which may suppress breast cancer growth and recurrence,? says lead researcher Michelle Holmes, M.D., of Harvard Medical School. In the study, as expected, women with hormone-sensitive tumors benefited the most from exercise.
The greatest benefit occurred in women who exercised the equivalent of walking three to five hours per week at an average pace. They experienced half the risk of recurrence of women who exercised less than one hour a week. That’s consistent with what the U.S. Dietary Guidelines for Americans recommend for lowering the risk of cardiovascular disease, diabetes, osteoporosis and other chronic illnesses. Higher levels of activity didn’t confer any additional benefit.
Another study of exercise and breast cancer survivors by Page Abrahamson, Ph.D., of the University of North Carolina at Chapel Hill, analyzed whether levels of activity before diagnosis influenced survival in a group of 1,263 women with invasive breast cancer.
The results? High levels of activity (the equivalent of walking 11 hours or more per week) in the year before diagnosis were associated with a 30% increase in breast cancer survival among overweight and obese women, compared to those who exercised less than one hour a week. No such link was found for women of normal weight.
Overweight women with breast cancer typically suffer higher death rates. Adding activity may be one way to increase the chances for long-term survival.
Exercise and Colon Cancer. Harvard’s Meyerhardt and colleagues at the Dana Farber Cancer Institute in Boston have conducted two studies of exercise and colon cancer recurrence.
In the first study, researchers evaluated the activity levels of 832 patients six months after surgery and chemotherapy for stage III colon cancer. They found that participants who exercised the equivalent of walking six or more hours per week at an average pace were only half as likely to suffer a recurrence compared to those who exercised less than one hour a week. Moreover, physical activity was linked to fewer deaths from all causes.
The team also studied 573 survivors of colon and rectal cancers from the Nurses? Health Study and found a similar protective benefit of exercise on cancer-related deaths and all other deaths.
Exactly how exercise might improve survival from colon cancer remains unclear. According to Meyerhardt, less recurrence is likely related to exercise’s ability to lower levels of substances known to drive cancer cell growth, such as insulin and insulin-like growth factor. Physical activity has also been associated with lower circulating levels of the inflammatory markers C-reactive protein and interleukin-6; high levels have been associated with increased cancer risk.
The Bottom Line. Although research on the role of physical activity in cancer recurrence is still evolving, it appears that exercise is beneficial, at least for breast and colon cancers. Moreover, leading an active lifestyle is critical for preventing obesity, which is a risk factor for a number of cancers, including cancers of the breast, colon, uterus and kidney.
Despite countless well-known health benefits of exercise, recent studies show that more than 60% of Americans are not active enough. For cancer survivors, a comprehensive long-term wellness plan should include a healthful diet, weight control and regular exercise, not only for upping the odds of staying cancer-free, but for reducing the risk of other chronic health threats, like cardiovascular disease and diabetes.