Association between physical activity and mortality among breast cancer and colorectal cancer survivors: a systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of prospective observational cohort studies
PubMed 24644304 · doi:10.1093/annonc/mdu012
What was done
A systematic review and random-effects meta-analysis of prospective cohort studies published through June 2013 evaluated the association between physical activity (pre- and post-diagnosis) and both total and cancer-specific mortality in breast and colorectal cancer survivors. The authors compared highest versus lowest activity categories, assessed linear dose-response relationships (per 10 MET-hours/week increase), and evaluated changes in physical activity from pre- to post-diagnosis.
What was found
The meta-analysis included 23 prospective studies (16 breast cancer, 7 colorectal cancer) comprising 49,095 survivors with 8,129 total deaths and 4,826 cancer-specific deaths. - Breast cancer survivors (highest vs lowest activity): - Pre-diagnosis: Summary relative risk (RR) was 0.77 (95% CI: 0.69–0.88) for total mortality and 0.77 (95% CI: 0.66–0.90) for breast cancer mortality. - Post-diagnosis: Summary RR was 0.52 (95% CI: 0.42–0.64) for total mortality and 0.72 (95% CI: 0.60–0.85) for breast cancer mortality. - Dose-response: Each 10 MET-h/week post-diagnosis increase reduced total mortality risk by 24% (95% CI: 11–36%). - Colorectal cancer survivors (highest vs lowest activity): - Pre-diagnosis: Summary RR was 0.74 (95% CI: 0.63–0.86) for total mortality and 0.75 (95% CI: 0.62–0.91) for colorectal cancer mortality. - Post-diagnosis: Summary RR was 0.58 (95% CI: 0.48–0.70) for total mortality and 0.61 (95% CI: 0.40–0.92) for colorectal cancer mortality. - Dose-response: Each 10 MET-h/week post-diagnosis increase reduced total mortality risk by 28% (95% CI: 20–35%). - Increasing physical activity from pre- to post-diagnosis versus remaining inactive or unchanged was associated with reduced total mortality across both cancers (RR = 0.61; 95% CI: 0.46–0.80).
Why it matters
This review provides quantitative evidence linking higher pre- and post-diagnosis exercise levels with substantially reduced all-cause and cancer-specific mortality in two common cancer types, supporting physical activity guidelines for cancer survivorship.
Limits
All included studies were observational cohorts rather than randomized controlled trials, leaving open the possibility of residual confounding and reverse causation (patients with more aggressive disease or worse treatment toxicity may exercise less). Physical activity was assessed via self-report across varied instruments, and specific exercise modalities, intensities, or potential interactions with cancer treatments were not detailed in the abstract.
Cited by
- supports Studies demonstrate that pre-diagnosis exercise is associated with improved post-diagnosis cancer survival outcomes, independent of post-diagnosis exercise.