Ben
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.”
