ABSTRACT
Objective To compare the setup errors of two position fixation, head-neck-shoulders immobilization system and trunk immobilization system in radiotherapy for esophageal cancer, and to provide technical guidance for the fixed modes and determination of plan target volume (PTV) in the intensity modulated radiation therapy (IMRT) of esophageal cancer. Methods 97 thoracic esophageal cancer patients treated with radiotherapy were collected and divided into two groups: head-neck-shoulders group (51 patients immobilized with head-neck-shoulders immobilization system) and trunk group (the other 46 patients immobilized with trunk immobilization system). Before the weekly radiotherapy, all the patients received cone-beam CT (CBCT) scan to get the setup errors of X axis (left and right), Y axis (head and foot) and Z axis (front and back) on line. Results In the head-neck-shoulders group, the errors in X, Y and Z direction were (0.333 ±0.400) cm, (0.333 ±0.291) cm and (0.238 ±0.256) cm, respectively. In trunk group, the errors were (0.327±0.255) cm, (0.582±0.501) cm and (0.189±0.154) cm, respectively. There were statistically significant differences in the setup errors in Y axis and Z axis between the head-neck-shoulders group and the trunk group (P< 0.05). Conclusions In the radiotherapy for thoracic esophageal carcinoma, there is no difference in the X axis setup error between head-neck-shoulders system and trunk immobilization system. The Y axis setup error of head-neck-shoulders group is less than that of the trunk group. The Z axis setup error of trunk group is less than the head-neck-shoulders group.