NEW YORK - People with colon cancer who spend more time walking and fewer hours on the couch are less likely to die over the seven to eight years after being diagnosed, a new study suggests.
The findings don't prove exercise itself boosts a person's survival chances, researchers said. But the pattern held even after the study team took into account how advanced patients' cancers were, their age and other aspects of their diet, lifestyle and health.
"Any activity is better than none," including walking, stretching and gardening, said Peter Campbell, the lead researcher on the study from the American Cancer Society.
"Five to ten minutes at a time is fine, and the type of activity we're talking about here, this isn't marathon running or climbing the Alps."
Campbell's analysis included about 2,300 people who developed colon cancer out of an initial pool of 184,000 volunteers in a cancer prevention and nutrition study launched in 1992.
Over an average of eight years after their diagnosis, 846 people with colon cancer died - including 379 from cancer.
The researchers found that study participants who exercised the most - equal to two and half hours of walking per week or more - both before and after being diagnosed were 28% to 42% less likely to die during the follow-up period than those who barely exercised at all.
Spending six or more hours of leisure time on the couch daily before diagnosis, compared to less than three hours, was tied to a 36% higher chance of dying. Being sedentary after a cancer diagnosis was linked to a 27% increased risk of death - although that particular finding could have been due to chance, the researchers noted this week in the Journal of Clinical Oncology.
To account for the fact that very sick people can't exercise, Campbell and his colleagues excluded anyone who died within two years of their last survey, and found similar results.
Researchers have known for a while that obesity and exercise affect a person's risk of getting colon cancer in the first place, said Dr. Jeffrey Meyerhardt from the Dana-Farber Cancer Institute in Boston, who has also studied exercise and colon cancer survival.
"The question when you're a patient with colorectal cancer is, ‘Do those things matter once I get the disease? Are there things I can do in addition to standard treatment to reduce my risk of recurrence?'" he told Reuters Health.
Researchers said there are a couple of possible explanations for why exercise, both pre- and post-diagnosis, might benefit people with cancer.
"What we think is at least part of what is happening is, people are going into surgery and adjuvant treatment in a more fit state," Campbell told Reuters Health.
In addition, he said, "If you're active both before and after diagnosis, there are a lot of changes that occur in your blood," such as in levels of insulin and other hormones.
"There are a lot of systemic changes that occur that probably decrease your chance of recurrence and ultimately dying."
People in the study who exercised regularly were less likely to die in general and of cardiovascular disease - such as heart attacks and lung disease - in particular. For those patients, exercise likely has the same benefit as for cancer-free people, Campbell said.
"Patients that have colon cancer, about two-thirds of them survive after five years and what they end up dying of is what all older people end up dying of, and that's usually cardiovascular disease."
He said people with colon cancer should discuss with their doctors when they can get back to physical activity. Some patients with anemia, for example, might want to hold off on exercise, and others who are immune compromised should probably avoid public gyms.
Meyerhardt recommended that people who exercised before their diagnosis return to that level of activity. Those who are new to exercise should take small steps toward increasing their activity, he added, such as walking and physical therapy.
However, Meyerhardt emphasized, exercise isn't a substitute for standard colon cancer treatments like surgery, and in some cases, chemotherapy.