Exercise capacity in long-term survivors of pediatric cancer: An analysis from the cardiac risk factors in childhood cancer survivors study

Background: Childhood cancer survivors may have premature symptomatic cardiovascular and non-cardiovascular diseases that contribute to reduced capacity for physical activity. Studies of exercise capacity and identification of risk factors for reduced capacity in survivors are limited. Procedure: We assessed maximal myocardial oxygen consumption (V_O2maxV_O2max, a measure of exercise capacity) in survivors at least 4 years after cancer diagnosis and sibling controls. We evaluated associations between V_O2max and age, sex, treatments, cardiac structure and function, biomarkers, endocrine function, and physical activity. Results: Of 72 survivors (mean age, 22 years; range, 8.0-40 years) and 32 siblings (mean age, 20.2 years; range, 8-46 years), about half were male. Mean time since diagnosis was 13.4 years (range, 4.5-31.6 years). In age- and sibling-pair adjusted analyses, V_O2max was lower in survivors than siblings (males, 28.53 vs. 30.90ml/kg/minute, P=0.08; females, 19.81 vs. 23.40ml/kg/minute, P=0.03). In males, older age (P=0.01), higher percent body fat (P<0.001) and high or low left ventricular (LV) mass Z-scores (P=0.03) predicted lower V_O2max. In females, older age (P<0.001), methotrexate exposure (P=0.01), and higher, but normal, LV load-dependent contractility (P=0.02) predicted lower V_O2max. Conclusions: Fitness for most survivors and controls was poor and generally lower in survivors, particularly females. Older age, higher body fat, methotrexate exposure, and extremes of LV mass/function were associated with lower V_O2max in survivors. Because physical activity can improve nutritional and cardiac conditions, survivors should be encouraged to exercise regularly with close monitoring.