TANGENTIAL BREAST IRRADIATION - RATIONALE AND METHODS FOR IMPROVING DOSIMETRY

In recent years there have been great advances and innovations in all technical aspects of radiotherapy, including three dimensional (3D) co mputer planning, patient immobilization, radiation delivery and treatm ent verification, Despite this progress, the technique of tangential b reast irradiation has changed little over this period and has not expl oited these advances. There is increasing evidence that dose inhomogen eity within the breast is greater than at other anatomical sites, espe cially in women with large breasts. This paper is a review of the fact ors contributing to poor dosimetry in the breast, the clinical consequ ences of an inhomogeneous dose distribution, and how breast dosimetry could be improved by considering each of the stages from planning to a ccurate treatment delivery. It also highlights the particular problem of women with large breasts who may be more likely to have a poorer co smetic outcome after a fractionated course of radiotherapy than women with small/medium-sized breasts, and supports the clinical impression that such women are also more likely to have greater dose inhomogeneit y when 3D treatment plans are examined. Preliminary data from our curr ent computed tomography (CT) planning study are presented to support t hese observations.