Dosimetric analysis of the partial breast irradiation technique depending upon various tumor locations; three dimensional conformal radiation therapy, electron beam therapy, helical tomotherapy

Partial Breast Irradiation (PBI) technique involves radiation beam delivery techniques that use a limited range of treatment volumes and is treatment approach as an alternative to whole breast irradiation technique. The present study was designed to propose the optimal treatment modalities for classified tumor locations into eight sections based on PBI treatment. Treatment planning was performed on the CT dataset of six patients who had received lumpectomy treatments. The tumor location was classified into eight sections according to the quadrants of breast and into the superficial, deep direction. 3D-conformal radiation therapy (3D-CRT), electron beam therapy (EBRT) and helical-tomotherapy (HTOMO) were utilized to evaluate dosimetric effect depending on each tumor location. For quantitative evaluation, Conformation Number (CN), radical Dose-Homogeneity and the dose delivered to healthy tissue were calculated. Kruskall-Wallis, Mann-Whitney U and Bonferroni method was applied as statistical analysis. In the analysis of the treatment planning for each modalities and tumor location, H-TOMO considered inactive method in PBI technique because no evaluation index achieved superiority in all tumor location except CN. Furthermore, the irradiated volume of heart received more than 2.5Gy was maximized above 90% in all tumor location during H-TOMO except Lower Outer Quadrant-Superficial case. However, EBRT showed good sparing effect, acceptable target coverage in Lower Inner Quadrant-Superficial (LIQ-S), Lower Inner Quadrant-Deep (LIQ-D) cases. Ultimately, EBRT could be advisable method to treat LIQ-S, LIQ-D cases rather than 3D-CRT, H-TOMO because of the acceptable target coverage and the greatly lower dose to surrounding tissue.