Objective: We aimed to evaluate the functional exercise capacity and its relation to echocardiographic measurements in pediatric cancer survivors who were treated with anthracyclines.

Material and Methods: Sixteen patients who completed chemotherapy 9-16 years ago and who have no symptoms of heart failure were enrolled in the study, together with 16 healthy subjects. Ejection fraction, fractional shortening, and myocardial performance index were calculated by echocardiographic evaluation. Patients with a myocardial performance index > 0.37 were accepted as having subclinical cardiotoxicity. Functional exercise capacity was evaluated by the sixminute walk test. results: Patients had significantly higher values of myocardial performance index than control subjects (p < 0.001). The six-minute walking distance was found to be lower in patients than that of the control subjects (p= 0.02). Furthermore, in patients with subclinical cardiotoxicity, the difference was more significant (p= 0.001). Six minute walking distance and myocardial performance index were well correlated with each other (r= -0.6 p= 0.03) and with cumulative anthracycline dosage (r= -0.6 p= 0.04 and r= 0.6 p= 0.02 respectively).conclusion: Long-term pediatric cancer survivors may have subclinicalcardiotoxicity despite having no clinical symptoms. Patients with subclinical cardiotoxicity should be taken into account for having impaired functional exercise capacity and correspondingly low quality of life. Six-minute walk test could be a useful indicator for subclinical cardiotoxicity since it is well correlated with myocardial performance index

Keywords: Activities of daily living, Anthracycline, Cancer, Children, Quality of life