ESTRO 2021 Abstract Book

S948

ESTRO 2021

Conclusion Whole breast hypofractionated forward-planned intensity modulated radiotherapy without boost after breast conservative surgery demonstrated good acute and late toxicity in this large cohort of 1325 consecutive patients. Approximately 10% of pts presented changes in breast appearance after radiotherapy. Breast volume and chemotherapy were the risk factors with a significant impact on toxicity. PO-1140 Reproducibility positioning in left side breast cancer patients with DIBH-SGRT-Catalyst system D. De La Mata Moya 1 , L.M.C. Tenorio Tellez 1 , S.L. Huerta 1 , A.S. Ramirez Astudillo 2 1 centro Medico Abc, Radiotherapy, Mexico City, Mexico; 2 centro Medico Abc, Radiotherapya, Mexico City, Mexico Purpose or Objective Twenty-nine breast cancer patients (p.) were treated with conformal (12p.) or VMAT (17p.) with DIBH. All patients were positioned using three tattoos in no breath hold cycle and Catalystâ C-RAD with DIBH adjustment, subsequently verified using Cone Beam Computed Tomography (CBCT) imaging for each fraction. A total of 529 movements were analyzed for the assessment of patient setup accuracy. The shift distribution along the three axis was analyzed. Materials and Methods Twenty-nine breast cancer patients (p.) were treated with conformal (12p.) or VMAT (17p.) with DIBH. All patients were positioned using three tattoos in no breath hold cycle and Catalystâ C-RAD with DIBH adjustment, subsequently verified using CBCT imaging for each fraction. A total of 529 movements were analyzed for the assessment of patient setup accuracy. The shift distribution along the three axis was analyzed. Results Error setup accuracy observed was within <3mm. margin. The mean movements registered were 0.09 mm. lateral (SD±0.46), 0.15 cm. vertical (SD±0.55) and 0.13 cm. longitudinal (SD±0.62) axis, when SGRT positioning procedure is used comparing CBCT analysis. The histograms of the longitudinal, lateral and vertical axis displacement vector are shown in figure 1.

Conclusion An excellent set up accuracy with SGRT-DIBH have been achieved during implementation in our institution. We consider SGRT and DIBH an useful tool for positioning patients without x-ray exposure, with the extra advantages of an easy workflow and quick integration.

PO-1141 Voluntary vs. mechanically induced DIBH for left breast cancer: a randomized trial L. Vander Veken 1,2 , G. Van Ooteghem 1,2 , E. Longton 2 , B. Ledoux 2 , C. Abdel Massih 2 , C. Delvaux 2 , P. Henderickx 2 , D. Dechambre 2 , A. Delor 2 , S. Da Rita Quaresma 2 , V. Aude 2 , X. Geets 2,1