Individually selected teletherapy technique for accelerated partial breast irradiation

Background: The aim of the study was to individualize accelerated partial breast irradiation based on optimal dose distribution, protect risk organ and predict most advantageous technique. Materials and methods: 138 breast cancer patients receiving postoperative APBI were enrolled. APBI plans were generated using 3D-conformal (3D-CRT), sliding window intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). In the case of superficial tumours, additional plans were developed by adding electron beam. To planning target volume (PTV) 37.5 Gy/10 fractions, 1 fraction/day was prescribed. A novel plan quality index (PQI) served as the basis for comparisons. Results: IMRT was the most advantageous technique regarding homogeneity. VMAT provided best conformity, 3D-CRT — the lowest lung and heart exposure. PQI was the best in 45 (32.61%) VMAT, 13 (9.42%) IMRT, 9 (6.52%) 3D-CRT plans. In 71 cases (51.45%) no difference was detected. In patients with large PTV, 3D-CRT was the most favourable. Additional electron beam improved PQI of 3D-CRT plans but had no meaningful effect on IMRT or VMAT. IMRT was superior to VMAT if the tumour was superficial (p < 0.001), situated in the medial (p = 0.032) or upper quadrant (p = 0.046). Conclusions: In half of all cases, individually selected teletherapy techniques provide superior results over others; relevance of a certain technique may be predicted by volume and PTV localization