RADIOTHERAPY OF BREAST-CANCER AFTER BREAST-CONSERVING SURGERY - AN IMPROVED TECHNIQUE USING MIXED ELECTRON-PHOTON BEAMS WITH A MULTILEAF COLLIMATOR

Background and purpose: Loco-regional radiotherapy after breast cancer surgery significantly reduces the risk of recurrences. An increase of cardiac deaths for irradiated breast cancer patients has been reporte d in some studies, especially for women with tumours in the left breas t. The aim of this study was to compare retrospectively the convention ally used technique using two opposed tangential photon beams with a m odified technique using a combination of photon and electron beams to find an optimal technique with respect to dose homogeneity in the brea st and surrounding regional lymph nodes and a minimal dose in the orga ns at risk. Materials and methods: Thirty patients with stage II breas t cancer who received different types of adjuvant systemic therapy wer e included in the investigation. Comparative dose planning of two tech niques was performed, i.e. an isocentric technique with two photon bea ms with coplanar medial beam edges and a technique with one electron a nd three photon beams with a common isocentre for all beams aided by a multileaf collimator. Results: The mixed technique was selected for e ight of 12 patients with left-sided breast cancers because of signific antly lower doses to the heart. However, the decision-making was influ enced by many factors such as dose coverage of the target volume combi ned with minimizing of the doses to the organs at risk and the contral ateral breast. Conclusion: The use of the mixed technique will optimiz e the loco-regional radiotherapy after breast-conserving surgery for m any left-sided breast cancers. (C) 1998 Elsevier Science Ireland Ltd.