Physical activity, risk of death and recurrence in breast cancer survivors: A systematic review and meta-analysis of epidemiological studies.
Level 3 - non-randomized controlled study
Systematic review of prospective observational cohort studies
PubMed 25752971 · doi:10.3109/0284186X.2014.998275
What was done
A systematic review and meta-analysis of PubMed, EMBASE, and CENTRAL databases up to October 18, 2014, was conducted to evaluate the relationship between physical activity and breast cancer recurrence or death. Prospective cohort studies reporting risk estimates for all-cause death, breast cancer-related death, or breast cancer recurrence across physical activity levels were included. Risk of bias was assessed with the Newcastle-Ottawa scale (NOS), and pooled hazard ratios (HR) and 95% confidence intervals (CI) were calculated using random-effects models.
What was found
Twenty-two prospective cohort studies (123,574 participants; 6,898 all-cause deaths; 5,462 breast cancer outcomes; average follow-up 4.3–12.7 years; mean NOS score 6, range 4–8) were analyzed: - High vs. low/no lifetime pre-diagnosis recreational activity: all-cause mortality HR = 0.82 (95% CI 0.70–0.96, p < 0.05); breast cancer mortality HR = 0.73 (95% CI 0.54–0.98, p < 0.05). - Recent pre-diagnosis recreational activity: all-cause mortality HR = 0.73 (95% CI 0.65–0.82, p < 0.001); breast cancer mortality HR = 0.84 (95% CI 0.73–0.97, p < 0.05). - Post-diagnosis physical activity: all-cause mortality HR = 0.52 (95% CI 0.43–0.64, p < 0.01); breast cancer mortality HR = 0.59 (95% CI 0.45–0.78, p < 0.05). - Post-diagnosis guideline adherence (≥ 8 MET-h/wk): all-cause mortality HR = 0.54 (95% CI 0.38–0.76, p < 0.01); breast cancer mortality HR = 0.67 (95% CI 0.50–0.90, p < 0.01). - Breast cancer events (progression, new primaries, recurrence): pre-diagnosis HR = 0.72 (95% CI 0.56–0.91, p < 0.01); post-diagnosis HR = 0.79 (95% CI 0.63–0.98, p < 0.05).
Why it matters
This review provides quantitative evidence that higher pre- and post-diagnosis physical activity levels are associated with substantially lower risks of all-cause mortality, disease-specific mortality, and disease recurrence in breast cancer survivors.
Limits
All included evidence comes from observational cohorts, making results susceptible to residual confounding and reverse causation. There was notable heterogeneity across lifetime pre-diagnosis and post-diagnosis analyses. Study quality varied considerably (NOS 4–8), and physical activity measures were self-reported.
Cited by
- supports Studies demonstrate that pre-diagnosis exercise is associated with improved post-diagnosis cancer survival outcomes, independent of post-diagnosis exercise.
- supports Epidemiological studies show that cancer patients who report more exercise have a lower risk of disease recurrence and a lower risk of dying from cancer.