In a study recently reported in Journal of Clinical Oncology, Peter T. Campbell, PhD, and colleagues from the Epidemiology Research Program of the American Cancer Society, Atlanta, found that more recreational physical activity before and after a diagnosis of colorectal cancer was associated with lower all-cause mortality, whereas longer leisure time spent sitting was associated with higher mortality.

Study Details

The study involved 2,293 patients from the Cancer Prevention Study-II Nutrition Cohort who did not have colorectal cancer at baseline in 1992–1993 but were diagnosed with invasive nonmetastatic colorectal cancer up through mid-2007. Participants completed detailed questionnaires including information about recreational physical activity and leisure time spent sitting at baseline and again after diagnosis of colorectal cancer.

During a maximum follow up of 16.1 years (mean, 6.8 years) after colorectal cancer diagnosis, 846 patients with colorectal cancer died, 379 of them from colorectal cancer, 152 from cardiovascular disease, 127 from other cancers, and 139 from other causes. All-cause, colorectal cancer–specific, and cardiovascular disease–specific mortality risks and risk from all other causes were analyzed according to recreational activity categories of < 3.5 (n = 255), 3.5 to < 8.75 (n = 943), and ≥ 8.75 (n = 1,064) metabolic equivalent (MET) hours per week and according to < 3 hours (n = 946), 3 to < 6 hours (n = 976), and ≥ 6 hours (n = 283) per day of leisure time sitting. A level of 8.75 MET h/wk corresponds to approximately 150 minutes of walking per week.

At baseline, there were significant differences across recreational activity MET categories for sex, education level, smoking, red meat intake, and body mass index, and no significant differences for age at colorectal cancer diagnosis, race, family history of colorectal cancer, leisure time spent sitting, hypertension, diabetes, colorectal cancer location, Surveillance, Epidemiology, and End Results (SEER) stage, tumor grade, or receipt of surgery, chemotherapy, or radiation therapy as first-line treatment.

For all comparisons, relative risks (RRs) were the adjusted values from multivariable analysis adjusting for age at diagnosis, sex, smoking status, body mass index, red meat intake, SEER stage, leisure time spent sitting, and education.  The postdiagnosis analyses excluded all patients dying within 6 months of reporting their postdiagnosis physical activity level.

Prediagnosis Activity and Leisure Time Sitting

For prediagnosis activity levels, patients in the middle activity category (3.5 to < 8.75 MET h/wk) had a significant 31% reduction in risk for all-cause mortality (RR = 0.69, 95% confidence interval [CI] = 0.55–0.85) and those in the highest category (≥ 8.75 MET h/wk) had a significant 27% reduction (RR = 0.72, 95% CI = 0.58–0.89) compared with those in the lowest category (< 3.5 MET h/wk).  The multivariable adjusted relative risks were consistently lower for the middle and highest physical activity categories vs the lowest category for colorectal cancer–specific mortality, cardiovascular disease–specific mortality, and mortality from all other causes. The only other statistically significant difference was a 32% reduction in risk for colorectal cancer–specific mortality in the middle activity category compared with the lowest activity category (RR = 0.32, 95% CI = 0.49–0.95).

For prediagnosis leisure time spent sitting, patients in the highest category (≥ 6 h/d) had a 36% increased risk of all-cause mortality (multivariable adjusted RR = 1.36, 95% CI = 1.10–1.68) compared with those in the lowest category (< 3 h/d). Those in the middle category had a nonsignificant 13% increased risk for all-cause mortality compared with those in the lowest category. Relative risks were consistently higher for patients in the middle and highest categories for colorectal cancer–specific mortality, cardiovascular disease–specific mortality, and mortality from all other causes. The only other statistically significant difference was a 48% increased risk for mortality from all other causes among patients in the highest category (RR = 1.48, 95% CI = 1.05–2.08).

Postdiagnosis Activity and Leisure Time Sitting

For postdiagnosis activity levels, patients in the highest group had a significant 42% reduced risk of all-cause mortality compared with those in the lowest group (RR = 0.58, 95% CI = 0.47–0.71). Patients in the middle group had a nonsignificant 22% reduction in risk. Relative risks for colorectal cancer–specific mortality were lower for the middle and highest groups, but the differences were not significant. Risk of cardiovascular disease–specific mortality was significantly reduced by 64% (RR = 0.36, 95% CI = 0.20–0.67) in the middle group and 64% in the highest group (RR = 0.36, 95% CI = 0.24–0.55). Risk of mortality from all other causes was significantly reduced by 50% in the highest group (RR = 0.50, 95% CI = 0.36–0.69). Relative risks for all other comparisons favored the middle and highest activity groups (except for a relative risk of 1.00 for colorectal cancer–specific mortality in the middle category).

For postdiagnosis leisure time spent sitting, the only significant effect observed was a 62% increased risk of colorectal cancer–specific mortality in patients in the highest category compared with those in the lowest (RR = 1.62, 95% CI = 1.07–2.44). Risk for all-cause mortality was nonsignificantly increased by 27% in the highest category.  For all other comparisons, relative risks indicated nonsignificantly increased risk in the middle and highest categories (except for a relative risk of 1.00 for cardiovascular disease–specific mortality in the middle category.

The authors noted that limitations of the study include lack of data on cancer recurrence, tumor molecular phenotype, and details of treatment beyond identification of first-line treatment. They stated, “Because all of the studies on this topic to date are observational, we cannot rule out the possibility that other factors associated with both physical activity and mortality and not assessed in these studies may be driving these apparent associations.”

The authors concluded, “[T]his study supports public health recommendations for recreational physical activity and the avoidance of sedentary time among colorectal cancer survivors. Clinically, physical activity recommendations should be based on the abilities and overall medical condition of a patient with cancer. Our results add to mounting evidence that physicians should consider counseling colorectal cancer survivors to adopt a physically active lifestyle aiming to achieve 150 minutes per week or more of moderate intensity activity, such as walking, and to avoid prolonged sitting.” ■

Disclosure:The authors reported no potential conflicts of interest.

Reference

1. Campbell PT, Patel AV, Newton CC, et al: Associations of recreational physical activity and leisure time spent sitting with colorectal cancer survival. J Clin Oncol 31:876-885, 2013.