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Reprinted from the NCI Cancer Bulletin, vol. 3/no. 29, July 18, 2006 (see the current issue ³).

In the studies, patients with early- to later-stage colorectal cancer (but not distant metastases) who engaged in regular activity after diagnosis decreased the likelihood of cancer recurrence and mortality by 40 to 50 percent or more compared with patients who engaged in little to no activity.

Released early online July 5, 2006, in the Journal of Clinical Oncology (and slated for print publication Aug. 1, 2006), the studies' results held true regardless of physical activity levels before cancer diagnosis or other factors that predict recurrence risk, such as the number of nearby lymph nodes harboring cancer cells.

The results, said the studies' lead author, Dr. Jeffrey A. Meyerhardt of the Dana-Farber Cancer Institute, may offer some important insight into why some colorectal cancer patients who receive standard-of-care treatments, including surgery and adjuvant chemotherapy, have recurrences, and some don't.

"One assumption has always been that it must be something about the molecular makeup of their tumor," he said. "This study implies that there are some lifestyle factors that may also have a significant effect on [treatment] outcomes."

The first study (see the journal abstract) involved 832 patients with stage III colorectal cancer who participated in a clinical trial led by the Cancer and Leukemia Group B ⁴ cooperative group that compared two adjuvant chemotherapy regimens.

On two occasions - four months after having their tumors surgically removed and then again 10 months later, well after adjuvant therapy was completed - participants provided detailed information about their diet and physical activity via a self-administered questionnaire. Only data from the second questionnaire were considered in the analysis.

Researchers converted the reports of physical activity (ranging from jogging to flights of stairs climbed) to metabolic equivalent task (MET) hours. For example, walking at a moderate pace for an hour is equivalent to three MET hours.

Compared with patients who reported less than three total MET hours per week, those reporting 18 to 26.9 and 27 or more had their risk of death from colorectal cancer reduced by 49 and 45 percent, respectively. In other words, six or more hours a week of walking at a moderate pace showed clear benefits.

The second study (see the journal abstract) followed a cohort of 573 participants in the long-running Nurses' Health Study ⁵ who, during the course of the study, were diagnosed with colorectal cancer.

Compared with participants who reported less than three MET hours of activity per week, those reporting 18 or more had their risk of death from colorectal cancer cut by 61 percent and their risk of death from any cause reduced by 57 percent.

In an accompanying editorial, Dr. Wendy Demark-Wahnefried of Duke University Medical Center noted that the risk reductions seen in these studies - as well as strikingly similar results reported last fall from a study of women with early-stage breast cancer - parallel "that of trastuzumab (Herceptin®) for HER 2-positive breast cancer patients."

Dr. Julia Rowland, head of the NCI Office of Cancer Survivorship, Division of Cancer Control and Population Sciences (DCCPS) ⁶, called the new studies "an important finding that adds to the evidence base on physical activity and cancer outcomes.

"They suggest that the time may be ripe to launch a randomized clinical trial of physical activity after cancer treatment," she continued. "To me, it opens up the door to an incredible wealth of science that, among other things, could help explain things like the interplay between behavior and underlying tumor processes."

NCI officials have already held preliminary discussions about the best settings for such a trial, she added, and how it might be designed.

By Carmen Phillips

Glossary Terms

Treatment given after the primary treatment to increase the chances of a cure. Adjuvant therapy may include chemotherapy, radiation therapy, hormone therapy, or biological therapy.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called a clinical study.

The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a “metastatic tumor” or a “metastasis.” The metastatic tumor contains cells that are like those in the original (primary) tumor. The plural form of metastasis is metastases (meh-TAS-tuh-SEEZ).

A type of study in which individuals are observed or certain outcomes are measured. No attempt is made to affect the outcome (for example, no treatment is given).

In medicine, a study or clinical trial in which participants are identified and then followed forward in time.

Cancer that has recurred (come back), usually after a period of time during which the cancer could not be detected. The cancer may come back to the same place as the original (primary) tumor or to another place in the body. Also called recurrence.

In medicine, treatment that experts agree is appropriate, accepted, and widely used. Health care providers are obligated to provide patients with the standard of care. Also called standard therapy or best practice.