Treatment of the chest wall

Irradiation of the chest wall is sometimes given following radical or modified radical mastectomy. The aim of treatment planning in such cases is to deliver a uniform dose to a superficial layer of tissue a few centimeters thick with an acceptably low dose to underlying tissues, particularly the lung. Both tangential photon beams and appositional electron beams have been used for this purpose, the choice between them being determined by the radiation modalities available, the extent and thickness of the designated target volume and the curvature of the patient's contour in the region. In this paper we will consider a few examples of both types of treatment with emphasis on the use of multiple electron fields. Dose distributions for the following plans were calculated using the system developed at the Cross Cancer Institute in Edmonton. In this system electron dose calculations are based on the Fermi-Eyges theory of multiple Coulomb scattering using the programs developed by Hogstrom and his co-workers.