Radiation pneumonitis in patients treated for breast cancer.

An analysis of 201 breast cancer patients having post-operative radiotherapy to the chest wall between January 1981 and May 1983 has identified those patients with chest symptoms following radiotherapy and these have been critically assessed with regard to the possibility of radiation pneumonitis being their cause. The inner contour of the anterior chest wall has been reconstructed on the radiation plan and the area of lung irradiated to a significant level in the mid-plane of the tangential fields determined. The incidence and severity of pneumonitis has been shown to rise exponentially with increase in the irradiated volume. A method of measuring the thickness of the chest wall using the simulator has been devised so that this information may be incorporated into the planning process in order to reduce the area of lung at risk.