PHYSICAL ACTIVITY DECREASES COLORECTAL CANCER MORTALITY 

Associations of Recreational Physical Activity and Leisure Time Spent Sitting With Colorectal Cancer Survival

Campbell PT, Patel AV, Newton CC, Jacobs EJ, Gapstur SM

J Clin Oncol. 2013;31:876-885

Study Summary

The association of physical activity with outcomes after a diagnosis of colorectal cancer is unknown, although it is clear that activity is associated with a reduced risk for incidence of colorectal cancer. In this report, the authors utilized a cohort of patients that had been established to study incidence of cancer in the early 1990s. They focused on 2293 patients who developed colorectal cancer during the follow-up period, which lasted a maximum of 16 years (until 2007). Patients with metastatic disease were excluded from the study. The authors examined associations between patient-reported activity, both pre- and post-diagnosis, with survival. Recreational physical activity was categorized as metabolic equivalent (MET) hours, corresponding to number of hours of walking per week:

• 3.5 MET hours = 1 hour of walking per week

• 3.5-8.74 MET hours = 1-2.5 hours of walking per week

• ≥ 8.75 MET hours = ≥ 2.5 hours of walking per week

• The investigators also evaluated sitting time and categorized this as < 3 hours per day, 3-6 hours per day, and ≥ 6 hours per day

Increased activity (≥ 8.75 MET hours vs < 3.5 MET hours per week) was associated with increased survival (prediagnosis physical activity: relative risk [RR], 0.72; 95% confidence interval [CI], 0.58-0.89; postdiagnosis physical activity: RR, 0.58; 95% CI, 0.47-0.71). Similarly, spending 6 or more hours per day of leisure time sitting compared with < 3 hours was associated with higher all-cause mortality (prediagnosis sitting time: RR, 1.36; 95% CI, 1.10-1.68; postdiagnosis sitting time: RR, 1.27; 95% CI, 0.99-1.64). Thus, activity levels both pre- and post-diagnosis are associated with outcomes in colorectal cancer.

Viewpoint

Sitting time and decreased activity levels are emerging as known risk factors, respectively, for colorectal and other cancers as well as cardiovascular disease. This study expands on the existing literature by demonstrating that both sitting time and activity levels affect outcomes after a diagnosis of colorectal cancer. The mechanisms underlying this association need to be further elucidated; possibilities include better tolerance of treatment, improved conditioning, reduction in cardiovascular diseases, and an effect on inflammatory markers. Regardless, these data further strengthen current recommendations to participate in at least 2.5 hours of walking per week for colorectal cancer survivors. Oncologists could frame increased activity as part of "adjuvant treatment."