Comparison Of Accelerated Partial Breast Radiation Therapy And External Beam Radiation Therapy By Treatment Planning Indices

BACKGROUND: Accelerated partial breast irradiation (APBI) is a method in which just bed of lumpectomy with a margin of 1–2 cm is irradiated. Regarding advantages of APBI to whole-brain radiation therapy (WBRT) and limitations for performing other techniques, we compare external beam radiation therapy (EBRT) with three-dimensional conformal radiation therapy (3DCRT), as a type of APBI technique. METHODS: Dosimetric parameters including uniformity index (UI), conformity index (CI), and homogeneity index (HI) beside heart and lung doses were assessed and compared in two techniques. CT images of 24 patients with left-sided breast cancer after lumpectomy were selected. Patients were categorized into three groups based on the volume of breast, respectively, ≤ 1000 cc, 1000–1500 cc, and ≥ 1500 cc. CI, HI, UI and DVH were calculated by DosiSoftIsogray treatment planning software. RESULTS: Results show the value of UI in APBI method is more than EBRT method significantly (p=0.004). Moreover, that CI in APBI method was more than EBRT (p=0.0000) and nearer to 1. There was no significant difference between HI values between APBI and EBRT methods. As the volume of breast gets bigger, HI values rise, meaning worse homogeneity. CONCLUSION: APBI method may be a good method for minimizing side effect and minimizing treatment periods.