ESTRO 2022 - Abstract Book

S927

Abstract book

ESTRO 2022

Estimated 3 and 5 year OS was 49% and 42%. On Univariate analysis the median OS in patients with GTVp < 30cc was better than GTVp >30cc (59.2 v/s 21.4 months, p=0.003); GTVn <4cc was better than >4cc (59.2 v/s 22.2 months, p=0.019); and GTVcombo <50cc was better than >50cc (59.2 vs 19.8 months, p=0.001).

Conclusion GTV should not just be limited for contouring but also has to be recognized as an important prognostic factor.

PO-1092 Clinical implication of different treatment techniques in glottic cancer

L. Cardoso 1 , S. Pena 2 , L. Gómez 1 , Á. Del Castillo 2 , M.L. Del Valle 1 , J.F. Gutiérrez 1 , M. Herrera 1 , M.I. Garavis 1 , A. Casado 1 , P. Valencia 1 , R. Jaraíz 1 , A. Hurtado 2 , P. Alonso 1 , I. Solis 1 , I. Conles 2 , D. Rodríguez 1 , M. Sánchez 1 , P. Diezhandino 1 1 Hospital Clínico Universitario de Valladolid, Radiation Oncology, Valladolid, Spain; 2 Hospital Clínico Universitario de Valladolid, Medical Physics, Valladolid, Spain Purpose or Objective Early stage glottic tumours (T1-T2 N0) have traditionally been treated with radical external radiotherapy (EBRT), showing 5 years local control rates of 80-90%. The classic treatment technique has been conformal 3D, but thanks to the emergence of techniques such as VMAT, the diversity in the choice of technique and treatment design has increased. The objective is to analyse the dosimetric discrepancies from data extracted from the DVH histogram for three types of treatment plans involving different techniques. Materials and Methods Nineteen patients with early squamous cell carcinoma of the glottis (T1-T2 N0) who received EBRT in our centre between January-2019 and September-2021 were selected retrospectively. All the cohort have one prescribed dose level of between 63-66 Gy and for each of them we performed three treatment plans with different techniques: 3D opposite field (3D), a full arc of intensity-modulated volumetric arc therapy (F-VMAT) and two partial-arcs butterfly VMAT (B-VMAT). 50% was treated with 3D, 25% VMAT and 25% B-VMAT. The treatment planning system used was Eclipse v15.6 and the algorithm AAA for 3D and AcurosXB 15.6.04 for VMAT. The median and the standard deviation of the maximum and of the average dose received by both carotids and the thyroid are analysed for the three treatment plans. Moreover, the median of the received by the spinal cord (SC) was also analysed. The volumes were contoured following RTOG guidelines, extending the volume of carotid arteries and spinal cord 2-1.5 cm above PTV and 1-1.5 cm below.