Can going for a walk improve cancer survivors' long-term prognosis? It may, according to new research showing that exercise can lower survivors' risk of premature death, not only from cancer but from any cause. The findings are likely to resonate widely at a time when about 14 million Americans, and many more worldwide, have survived cancer.
In one report, a major new review published this month in The Journal of the National Cancer Institute, scientists at the agency gathered available studies examining exercise and cancer survivorship, dating to 1950. Most had been published in the past five years.
"This is an area of growing scientific interest," says Dr. Rachel Ballard-Barbash, the associate director for applied research at the National Cancer Institute and lead author of the study. "Exercise is an accessible, low-cost intervention. But before we can suggest that cancer survivors become physically active, we need to understand what effects exercise has" on the bodies and life spans of those who've been given a cancer diagnosis.
To date, messages about the effects of exercise on cancer patients have been mixed. Some physicians have worried that exercise might exacerbate the fatigue that is common after cancer treatment. Others have raised concerns that the physical stress of exercise could even create conditions within the body that might contribute to tumor recurrence.
A 2010 roundtable convened by the American College of Sports Medicine concluded that exercise appeared to be safe for most cancer survivors, but anyone whose treatment had involved drugs harmful to the heart muscle or bone density should be closely monitored. But those recommendations didn't directly address the issue of whether or how exercise might affect tumor recurrence or to what degree exercise could affect a survivor's overall life span.
So those became the concerns that Dr. Ballard-Barbash and her colleagues set out to examine in more detail.
In the end, they found 45 studies that looked at physical activity among people who'd received a diagnosis of cancer. The types of tumors studied included prostate, ovarian, brain and colorectal. But a majority of the studies, "as in most cancer research," involved women who had survived breast cancer, Dr. Ballard-Barbash said. "There's a lot of research money in that field," so, in general, there is more available science.
Most of the studies also were observational, meaning that patients completed questionnaires about their activities, which can be unreliable since people may not accurately recall their true activity levels. Only a few were actual experiments, during which volunteers were assigned to exercise or to remain sedentary. And although none were designed expressly to determine what biochemical or genetic effects exercise might be having on cells within the body, several did look at various biomarkers that have been found to play a role in cancer recurrence and progression.
As it turned out, virtually all of the studies, whatever their methodology, showed that regular physical activity "decreased the risk of cancer-related mortality and of all-cause mortality," Dr. Ballard-Barbash said.
Exercise, in other words, made it less likely that a survivor would subsequently die from a recurrence of his or her cancer. When Dr. Ballard-Barbash and her colleagues teased out specific information about biomarkers related to cancer recurrence, they found that exercise tended reliably to improve insulin levels, reduce inflammation and increase populations of the very immune system cells that are thought to attack tumors.
Exercise also lessened the chances that a survivor of cancer would later succumb prematurely to other common diseases like heart disease or diabetes. "We live in an era when cancer has moved away from being generally fatal to being itself a chronic disease," Dr. Ballard-Barbash said. People can live many years after a cancer diagnosis. "If they are inactive," she continued, "they risk developing other chronic diseases."
Exercise made the cancer survivors in the studies she and her colleagues examined healthier and far more likely to enjoy a longer life span than if they were sedentary, although she cautioned that the patients who exercised may have been in better health or faced a less aggressive cancer to begin with.
Interestingly, exercise did not seem to increase fatigue among most survivors. More often, it lessened it.
Researchers found similar results in another new study published this month, this one involving colorectal cancer survivors in the Netherlands. Those who exercised reported much less exhaustion and, in general, greater health-related quality of life than those who did not. "Fatigue and the fear of tiredness may be a barrier to physical activity for some people" who've survived cancer, said Laurien M. Buffart, a professor at VU University Medical Center in Amsterdam, who led the study. "But more and more evidence suggests the reverse," that exercise energizes people who are undergoing or have completed cancer treatment.
And the exercise does not need to be intimidating or vigorous. "In our review, the most common activity was walking," Dr. Ballard-Barbash said, "which happens to be an activity that is within the scope of almost anyone."
She added that many more experiments are needed to determine the ideal dose and type of exercise to improve long-term survival after cancer treatment. Survivors also should consult a physician, of course, about the effects of treatment on the heart or about their readiness, in general, to exercise. But if you get the go-ahead, she said, "it appears that any activity," in any amount, "is beneficial for those who've had cancer."
http://well.blogs.nytimes.com/2012/05/16/cancer-survivors-who-stay-active-live-longer/?emc=eta1
