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Exercise Helps Patients Beat Colorectal Cancer
MedPage Today Published: December 14, 2009
Action Points
* Explain to interested patients that even after a colorectal cancer diagnosis, patients in this study who exercised the most had the least risk of dying from their disease.
* Inform cancer patients that the benefits of exercise may continue despite their illness.
* Discuss with cancer patients appropriate forms of exercise (aerobic versus low-intensity) and optimal time to begin an exercise regimen.
Men with nonmetastatic colorectal cancer who exercised regularly were less than half as likely to die from the disease as sedentary patients, researchers at the Dana-Farber Cancer Institute reported.
Patients whose exercise habits fell into the highest category showed a 53 percent lower colorectal cancer death rate (adjusted HR 0.47, 95% CI 0.24 to 0.92, P=0.002 for trend), and a 41 percent lower death rate overall (HR 0.59, 95% CI 0.41 to 0.86, P<0.001) than men who exercised the least.
The findings, published in Dec. 14/28 Archives of Internal Medicine, suggest that regular physical activity can still have an impact on overall health even after a cancer diagnosis, lead author Jeffrey A. Meyerhardt, MD, MPH, told MedPage Today.
The benefits accrued regardless of patients' age, disease stage, body mass index, year of diagnosis, tumor location, and prediagnosis physical activity status, the researchers reported.
It's not clear whether the exercise itself produces the benefit, since it may also be a sign of a generally healthy lifestyle that includes a balanced diet and eschews smoking.
"For these types of studies, it is very true confounders are very important to consider," Meyerhardt said. "In our analyses, we do adjust for confounders like body mass index and smoking."
The results, he added, provide further evidence that physical activity after colorectal cancer diagnosis may lower the risk of death from that disease.
The findings are based on records of 668 men with either stages I, II, or III colorectal cancer who were part of the Health Professionals Follow-up Study. The men had no apparent metastases at the time of their diagnosis. Treatment data were not collected for this group.
Patients were questioned every two years to report any new cancer and disease diagnoses as well as physical activities, including walking, biking, yoga, and other types of aerobic or low-intensity exercises.
Each physical activity was assigned a metabolic equivalent task (MET) score, defined as the ratio of the metabolic rate associated with specific activities divided by the resting metabolic rate. More intense activities had higher MET scores.
About half of the group reported exercising at least 18 MET hours per week.
A total of 258 men died during the study, including 88 deaths attributed to colorectal cancer.
Patients who experienced cancer recurrences or who died within six months of having their physical activity assessed were excluded from the study.
Even when this restriction was extended to 12 months, the inverse dose relationship between exercise and colorectal cancer recurrence and/or death remained.
In addition to the absence of data on treatment, the study was limited by lack of data on cancer recurrence.
Colorectal cancer risk is higher among patients with elevated insulin. Meyerhardt and colleagues suggested that the impact of exercise on insulin levels may, in turn, affect insulin-like growth factor (IGF), which has been associated with promoting tumor growth and lowering overall tissue insulin and IGF levels.
It is also possible, they added, that exercise might promote anti-inflammatory responses.
The timing of exercise may also be a factor, although Meyerhardt said the optimal time to start is not clear and cancer patients may face limitations in their abilities to exercise right after surgery or during chemotherapy.
In this study, "some people who didn't exercise much prior to diagnosis did more after," Meyerhardt said in an interview. "Second, the level [of exercise] prior to diagnosis did not impact as much as the level after diagnosis, implying starting after diagnosis can be beneficial."
In an accompanying commentary, Janet E. Fulton, PhD, of CDC's Division of Nutrition and Physical Activity, and colleagues noted that there is little in the literature shedding light on the science behind physical activity and its relationship to health and disease.
"The findings of Meyerhardt et al are important because they add to the limited science base on physical activity and recurrent colorectal cancer risk and because they suggest that a relatively large dose of physical activity may provide the greatest benefit in cases of recurrent colorectal cancer," they write.
"To provide direction for future public health guidelines, it will also be important to compare the disease risks that are associated with the recommended minimal amount of aerobic activity (150 minutes/week, moderate intensity) and the amount recommended for additional health benefits (300 minutes/week, moderate intensity)."
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