Partial irradiation of the heart

Radiation-induced heart disease (RIHD) includes pericarditis, ischemic heart disease, and myocardial infarction and leads in some cases to fatal complications. It has been shown that the increased survival due to radiotherapy could be negated by excess deaths from RIHD in breast cancer radiotherapy for left-sided tumors. Subclinical effects following irradiation have been detected in several studies both of breast cancer and Hodgkin's irradiation. The dose-volume response relationships describing cardiac complications have been studied for pericarditis and cardiac mortality by means of biologic models, including the well-known Lyman-Kutcher-Burman (LKB) model and Källman's relative seriality model. Studies by Martel and coworkers on pericarditis and by Gagliardi and coworkers on cardiac mortality are reviewed. The anatomical and functional definition of the heart represents a key issue in modeling, as it affects strongly the dosimetrical data to be used as input data in the models. Several treatment strategies to decrease heart irradiation, based on models and/or based on dose-distribution evaluations, are reviewed. It is concluded that left-sided breast cancer patients should always be 3-dimensional (3D) dose planned.