[Clinical and methodological aspects of quality assurance in external radiotherapy: optimization of radiotherapy in early cancer of the breast]

Abstract

Since 1988, a specific physical and clinical quality assurance program for external whole breast irradiation has been activated in our department. Three areas of clinical investigation and related audit loops are analyzed to show our policy to improve the quality of patient care. Quality control procedures deal with (a) the evaluation of the adequacy of conventional methods of clinical target volume (CTV) localization, (b) the evaluation of the adequacy of the conventional method of determining the planning target volume (PTV) and (c) the systematic and objective assessment of acute and late side-effects. Corrective actions to maintain or meet the standards are also reported. The localization of residual mammary gland using conventional methods (anatomy and/or palpation) was compared in 100 patients with US localization: conventional methods were often inadequate and thus the use of US in PTV determination is necessary. Portal film analysis helped reduce ideal margins from 20 mm to 11 mm. The amount of irradiated ispilateral lung, retrospectively calculated in 88 consecutive patients, appeared adequate to the chosen reference standard. The systematic study of late skin reactions had shown in some patients telangectasia regions outside the boost area: since 1991, a corrective action, decreasing the thickness of the customized immobilization cast inside the treatment area, from 2 mm to 0.2 mm, has been adopted. These examples show that the routine application of quality assurance procedures can help optimize radiation treatment.