Quality assurance in tangential breast irradiation

Early breast cancer patients are treated with breast conserving methods: excision of the tumor and axillary clearance and radiotherapy to the breast. Outcome of breast conserving treatment, in terms of local control, cosmesis and complication rate, depends on the quality of surgery and on the adequacy of irradiation treatment performed. Adequate radiation treatment prescription consists of the definition of the target volume, total dose, total treatment time and fraction size, as well as a proposal for beam energy and treatment technique. Often complex irradiation techniques are used for several reasons: -Tangential irradiation techniques are required in order to spare underlying lung tissue, thus avoiding functional lung damage; -Regional lymphnodes are to be treated with additional treatment portals, leading to problems of field direction and field alignment and if not performed in a proper way, affecting cosmetic outcome; -The breast is an irregular volume and adequate beam energy and tissue compensators are to be used to avoid large dose inhomogeneity throughout the breast; -Adequate immobilisation of the patients in treatment position is mandatory to ensure a reproducible daily treatment set-up; -In many cases a booster dose is delivered to the primary tumor area. The choice on the boost technique is largely dependent on localisation of the primary tumor in the breast and will be different for superficial or deeply seated tumors. (author). 14 refs