Association between cardiac substructure radiation dose and risk of late cardiac disease in survivors of childhood cancer

Radiation-associated cardiac disease is a major cause of morbidity and mortality among childhood cancer survivors (CCSs). Analysis of 25.481 5-year CCSs treated from 1970 to 1999 found that mean doses of 5.0-9.9 Gy to the whole heart did not increase the 35-year cumulative incidence of any cardiac diseases, suggesting a potential threshold dose. However, this was not the case for radiation exposure of cardiac substructures. Mean doses of 5.0-9.9 Gy to the right coronary artery and left ventricle increased risk of coronary artery disease, and mean doses of 5.0-9.9 Gy to the tricuspid valve and right ventricle increased the risk of valvular disease. The authors conclude that the analysis suggests that among children with cancer, there may be no threshold dose below which radiation to cardiac substructures does not increase the risk of cardiac diseases.