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(O(2)max), a measure of exercise capacity) in survivors at least 4 years after cancer diagnosis and sibling controls. We evaluated associations between V(O(2)max) 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(O(2)max) was lower in survivors than siblings (males, 28.53 vs. 30.90 ml/kg/minute, P = 0.08; females, 19.81 vs. 23.40 ml/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(O(2)max). 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(O(2)max).
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(O(2)max) in survivors. Because physical activity can improve nutritional and cardiac conditions, survivors should be encouraged to exercise regularly with close monitoring.