Organ motion study and dosimetric impact of respiratory gating radiotherapy for esophageal cancer ; Etude de mobilité organique et impact dosimétrique de l'asservissement respiratoire dans la radiothérapie des cancers de l'oesophage

Chemoradiotherapy is now the standard treatment for locally advanced or inoperable esophageal carcinoma. In this indication, conformal radiotherapy is generally used. However, prognosis remains poor for these patients.Respiratory gating radiotherapy can decrease healthy tissus irradiation and allows escalation dose in lung, liver and breast cancer. In order to improve radiotherapy technique, we propose to study the feasibility of respiratory gating for esophageal cancer.We will study the respiratory motions of esophageal cancer to optimize target volume delineation, especially the internal margin (IM).We will test the correlation between tumour and chest wall displacements to prove that esophageal cancer motions are induced by respiration. This is essential before using free breathing respiratory gating systems.We will work out the dosimetric impact of respiratory gating using various dosimetric analysis parameters. We will compare dosimetric plans at end expiration, end inspiration and deep inspiration with dosimetric plan in free-breathing condition. This will allow us to establish the best respiratory phase to irradiate for each gating system.This dosimetric study will be completed with linear quadratic equivalent uniform dose (EUD) calculation for each volume of interest. Previously, we will do a theoretical study of histogram dose volume gradation to point up its use ; La chimioradiothérapie est le traitement des cancers de l'oesophage localement évolués et inopérables. Dans cette indication, la radiothérapie conformationnelle est utilisée couramment. Cependant, le pronostic de ces patients reste sombre. L'intérêt de la radiothérapie asservie à la respiration (RAR) a déjà été montré notamment dans le traitement des cancers pulmonaires, mammaires et hépatiques : elle permet de diminuer l'irradiation des tissus sains, et d'envisager une augmentation de dose au volume tumoral. Afin d'améliorer la prise en charge radiothérapique, nous proposons d'étudier la faisabilité de la RAR dans le traitement des cancers ...