ESTRO 2021 Abstract Book

S926

ESTRO 2021

PO-1113 A dosimetric comparison of two external beam radiotherapy techniques: 3DCRT & Tomotherapy in APBI R. Rajan 1 , B. Kunheri 1 , S. N 2 , G. C R 3 1 Amrita Institute of Medical Sciences, Department of Radiation Oncology, Kochi, India; 2 Amrita Institute of Medical Sciences, Department of Radiation Physics, Kochi, India; 3 Amrita Institute of Medical Sciences, Department of Biostatistics, Kochi , India Purpose or Objective To prospectively analyse and compare the pertinent dosimetric parameters of two different external beam radiation therapy techniques for accelerated partial breast irradiation ; Three- dimensional conformal radiotherapy (3DCRT) versus Tomotherapy (TOMO) in early stage breast cancer. Materials and Methods The study included 30 patients with carcinoma of the breast who satisfied the following criteria (1) Undergone lumpectomy and nodal evaluation with negative surgical margins (2) ASTRO recommended tumour size criteria (T size ≤ 3cm) for APBI. Plans were generated for each technique using the Xio (Elekta) TPS for 3DCRT plans and Precision (Accuray) TPS for Tomotherapy plans. Dose prescribed was 38.5Gy in 10 fractions. Based on the NSABP B-39/RTOG 0413 protocol, a separate PTV was created to allow a DVH comparison (PTV_EVAL). To test the statistical significant comparison of dosimetry between the two techniques, paired t test was applied for parametric data and Wilcoxon signed rank test was applied for non-parametric data. A p-value <0.05 was considered to denote statistical significance.