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SAN FRANCISCO - Increased physical activity had a significant association with improved survival in metastatic colorectal cancer, data from a prospective cohort study showed.

Patients who engaged in at least 5 hours of non-vigorous physical activity a week had a 25% reduction in the hazard for survival. With 4 or more hours of weekly activity, the survival hazard improved by 20%.

As little as 30 minutes of daily activity reduced the risk of disease progression and death, , of Brigham and Women's Hospital in Boston, said during a press briefing prior to the , which begins here Thursday.

"In this prospective cohort study of metastatic colorectal cancer patients, increasing total physical activity was associated with improved progression-free survival and overall survival," said Guercio. "Greater walking duration -- but not walking pace -- and non-vigorous activity were also associated with improved overall survival. These associations remained statistically significant after adjusting for other potential predictors of patient outcome."

The study is the first to demonstrate a physical activity-associated survival benefit in metastatic colorectal cancer, according to Guercio and his colleagues.

The findings are particularly noteworthy because the activity level evaluated in the study did not set the bar unrealistically high for patients with metastatic colorectal cancer, according to webcast moderator , a scientific expert for the American Society of Clinical Oncology, co-sponsor of the symposium.

"Physical activity can be difficult for patients with advanced colorectal cancer, but this study shows that even a small amount of exercise may make a big difference," said Baxter, of the University of Toronto and St. Michael's Hospital, in a statement. "It's important to help our patients find ways to incorporate moderate exercise into their daily lives -- regardless of the stage of their disease."

The data are consistent with previous studies in nonmetastatic settings of colorectal cancer. For example showed that a person's level of physical activity prior to diagnosis had a significant association with survival. Multiple studies consistently showed that increased physical activity after diagnosis of colorectal cancer improved survival.

Other studies showed that the risk of developing colorectal cancer decreases as physical activity increases. Similar data have been reported for other types of cancer.

To investigate the association between physical activity and outcome in metastatic colorectal cancer, Guercio's group reviewed data from a prospective cohort study nested within the Cancer and Leukemia Group B (now the Alliance for Clinical Trials in Oncology) 80405 randomized trial.

The trial's was to evaluate the addition of biological agents chemotherapy for patients with metastatic colorectal cancer. However, the 1,231 patients enrolled in the trial provided information about baseline physical activity, which provided the basis for the study and analysis reported by Guercio. Patients completed a baseline activity questionnaire that covered nine leisure-time activities and the study participant's average walking pace.

The primary objective of both the main trial and the cohort study was overall survival. Progression-free survival was a key secondary outcome of both analyses.

Guercio reported that total physical activity equivalent to 30 or more minutes of moderate activity daily was associated with a 21% reduction in the risk of disease progression (HR 0.79, 95% CI 0.67-0.93, P=0.003) and a 29% reduction in the risk of death (HR 0.71, 95% CI o.59-0.85, P=0.003).

Total physical activity equivalent to 4 or more hours weekly was associated with a 20% improvement in survival. Increasing total weekly activity to at least 5 hours improved the survival hazard by 25%.

Guercio emphasized that the benefits were observed with non-vigorous activity, such as walking or yoga. The investigators thought that walking pace might also have a favorable impact on survival, but that proved not to be the case.

Following an analysis of the raw (unadjusted) data, investigators took another look, controlling for a variety of potential confounders, including comorbidities, weight change over the previous 6 months, performance status body mass index, type of chemotherapy received, tumor KRAS status, patient sex, and age.

"We wanted to see whether physical activity helped make people healthier or did our findings merely indicate that sicker individuals exercised less," said Guercio.

The principal findings retained statistical significance in the fully adjusted analysis. Individuals who, on average, engaged 30 minutes of non-vigorous physical activity daily had a 16% reduction in the hazard for disease progression (HR 0.84, 95% CI 0.71-1.00, P=0.03). The survival hazard remained 19% lower (HR 0.81, 95% CI 0.67-0.98, P=0.03).

"These findings suggest that it doesn't take a lot of physical activity to improve outcomes," said Guercio. "While exercise is by no means a substitute for chemotherapy, patients can experience a wide range of benefits from as little as 3o minutes of exercise a day."

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