SU-E-T-566: A Dosimetric Comparison of Partial Breast Irradiation Technique Depending on the Tumor Locations in Patient's Breast.

PURPOSE: The present study was designed to suggest the optimal treatment modalities among 3D-conformal radiation therapy, electron beam therapy and helical-tomotherapy depending on classified tumor locations in patient's breast using Partial Breast Irradiation (PBI) technique.

METHODS

The CT dataset of six patients who had received lumpectomy treatments was used to treatment plans of 3D-conformal radiation therapy, electron beam therapy and helical-tomotherapy. The tumor locations were classified into eight sections according to the quadrants of the breast and to the superficial or deep positions. To evaluate the dosimetric results from the suggested treatment modalities and tumor locations, conformation number, radical dose-homogeneity and delivered doses to normal tissue were calculated. Kruskall-Wallis, Mann-Whitney U and Bonferroni method was used as statistical analysis.

RESULTS

Helical-tomotherapy is not recommendable method in PBI technique because the dosimetric results from radical dose- homogeneity and the delivered dose to organ at risk showed worse results at all tumor locations compared to other modalities. For helical-tomotherapy, the volume of heart received more than 2.5 Gy was maximized more than 90% of total heart volume at all tumor locations. Electron beam therapy showed good sparing effect to normal tissues and acceptable target coverage in Lower Inner Quadrant-Superficial (LIQ-S) and Lower Inner Quadrant- Deep (LIQ-D) cases.

CONCLUSIONS

Electron beam therapy could be recommendable method to treat tumor at LIQ-S, LIQ-D locations rather than 3D-conformal radiation therapy, helical-tomotherapy at PBI technique because electron beam therapy is considered to provide the acceptable target coverage and the greatly lower dose to surrounding tissue.