Investigation of the effect of patient respiratory action on dose distribution in esophageal cancer radiotherapy with different planning techniques

Esophageal cancer is one of the most common malignant tumor types worldwide. Currently, complete surgical resection is the standard treatment for patients with esophageal cancer who are medically appropriate. Radiotherapy is a critical component in the multimodality systemic treatment of esophageal cancer. For thoracic esophageal cancer, displacement and deformation caused by respiratory motion are critical factors affecting treatment accuracy and precision. It has been observed in many studies that active respiratory control practice reduces movement caused by breathing. In this study, three-phase active breathing controlled radiotherapy of esophageal carcinoma with free-breathing, deep inspiration(DIBH), and expiration was performed using 3-dimensional conformal(3DCRT), intensity-modulated radiotherapy(IMRT), and volumetric arc therapy(VMAT) techniques. It was aimed to create treatment plans, investigate the effect of respiratory movements on dose distribution and compare the advantages of techniques in terms of the target volume and critical organ doses. Computed tomography(CT) images of 10 patients with esophageal cancer used in our thesis were taken with 3 different respiratory phases. Treatment plans were prepared using the same criteria for each patient, the conformity and homogeneity index(HI-CI) of the plans were calculated, the dose values and treatment durations received by PTV and critical organs(OAR) were compared. Consequent to our study, independent of the techniques used, it was observed that critical organ doses decreased with the method of DIBH. This method can be considered as a reliable technique in the treatment of patients who may cooperate with breathing control systems.VMAT is a preferred radiotherapy technique for esophageal cancer irradiation with high dose conformity-homogeneity, better protection of OAR, and shorter treatment duration.