[Cardiac complications of radiotherapy]

Radiotherapy is an effective tool in the treatment of thoracic cancers. However, radiotherapy also carries a risk of severe cardiac complications. The cancers most commonly concerned are Hodgkin's and non-Hodgkin's lymphomas (90 per cent of cases), breast cancers, especially on the left side (4 per cent) and bronchogenic cancers (2 per cent). Ionizing radiation can damage the three layers of the heart and the coronary arteries. Pericardial involvement is the most frequent, occurring in 10 to 12 per cent of cases. It generally occurs 6 to 18 months after the radiotherapy and may present either acutely (35 per cent of cases) or chronically (65 per cent of cases). It is often latent, only detected on X-rays or on ultrasound. Constrictive forms can occur, which require pericardiectomy. Myocardial fibrosis, which is anatomically common, may present as disturbances of repolarization, arrhythmia or disturbances of conduction, or even cardiac failure. Rarely, radiation damage of the coronary arteries can cause angina or myocardial infarction. These cases can benefit from coronary artery by-pass grafts. All of these lesions have a common anatomical denominator:fibrosis, which develops progressively following the radiotherapy. It has now been demonstrated that the incidence of cardiac radiation lesions can be reduced by homogeneous distribution of the dose of radiation administered to the mediastinum, by treating each side alternately, by fractionating the radiation and staggering the sessions and by reducing the cardiac mass which is irradiated.