Clinical dosimetry for radiotherapy to the breast based on imaging with the prototype Royal Marsden Hospital CT simulator.

The result of conservative management of breast cancer is strongly dependent on the homogeneity of the dose delivered a schedule of post-surgical radiotherapy. In addition to improvements in local control, late normal-tissue effects should be minimised by achieving a good dose homogeneity. The Royal Marsden Hospital prototype CT simulator has been used to image patients in the treatment position. With the CT data incorporated into the planning process a quantitative measure of the dose homogeneity was made. There are strong indications that unless tissue compensators are used and/or conformation therapy is performed, the dose inhomogeneity in a widely used treatment geometry is too large to be clinically acceptable.