Association of post-diagnosis cardiorespiratory fitness with cause-specific mortality in cancer.

AIMS: The prognostic importance of post-diagnosis assessment of cardiorespiratory fitness (CRF) in cancer patients is not well established. We sought to examine the association between CRF and mortality in cancer patients. METHODS AND RESULTS: This was a single-centre cohort analysis of 1632 patients (58% male; 64 ± 12 years) with adult-onset cancer who were clinically referred for exercise treadmill testing a median of 7 [interquartile range (IQR): 3-12] years after primary diagnosis. Cardiorespiratory fitness was defined as peak metabolic equivalents (METs) achieved during standard Bruce protocol and categorized by tertiles. The association between CRF and all-cause and cause-specific mortality was assessed using multivariable Cox proportional hazard models adjusting for important covariates. Median follow-up was 4.6 (IQR: 2.6-7.0) years; a total of 411 deaths (229, 50, and 132 all-cause, cardiovascular (CV), and cancer related, respectively) occurred during this period. Compared with low CRF (range: 1.9-7.6 METs), the adjusted hazard ratio (HR) for all-cause mortality was 0.38 [95% confidence interval (CI): 0.28-0.52] for intermediate CRF (range: 7.7-10.6 METs) and 0.17 (95% CI: 0.11-0.27) for high CRF (range: 10.7-22.0 METs). The corresponding HRs were 0.40 (95% CI: 0.19-0.86) and 0.41 (95% CI: 0.16-1.05) for CV mortality and 0.40 (95% CI: 0.26-0.60) and 0.16 (95% CI: 0.09-0.28) for cancer mortality, respectively. The adjusted risk of all-cause, CV, and cancer mortality decreased by 26%, 14%, and 25%, respectively with each one MET increment in CRF. CONCLUSION: Cardiorespiratory fitness is a strong, independent predictor of all-cause, CV, and cancer mortality, even after adjustment for important clinical covariates in patients with certain cancers.