Objective To compare the set-up errors of mid-thoracic esophageal cancer treated with three different radiotherapy immobilization methods and to analyze its influence on the set-up errors of the supraclavicular and infraclavicular region.

Methods A total of 73 mid-thoracic esophageal cancer patients with supraclavicular lymph node metastasis treated from November 2019 to November 2021 at the Cancer Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College were retrospectively reviewed. The sample included 56 males and 17 females, with a median age of 63.6 (36.5−85.3) years. Of these, 24 patients were fixed with a thoracoabdominal flat frame, with both hands crossed on the forehead and 25 had both of their hands placed on the sides of their bodies. In addition, 24 patients were fixed with integrated cervicothoracic immobilization devices with both their hands on the sides of their bodies. Cone beam CT (CBCT) scans were performed once a day at the first five workdays and once a week in the following treatment time. Translational set-up errors in the (X direction) left and right, (Y direction) cranial and caudal, (Z direction) ventral and dorsal directions within the compared target volumes were recorded. The translational set-up error of the three modes of immobilization were compared, and the amplitudes of movement and the three-dimensional spatial displacement of the acromioclavicular joint were measured. Independent sample t-test or Wilcoxon rank sum test were employed to analyze the error values between groups.

Results A total of 208, 195, and 195 CBCT scans were performed in the thoracoabdominal flat frame elevation, the thoracoabdominal flat frame side, and the integrated cervicothoracic immobilization device side groups, respectively. The translational set-up errors of the three groups were recorded for the left and right directions: (0.19±0.15), (0.16±0.15), and (0.14±0.14) cm; the cranial and caudal directions: (0.30±0.24), (0.27±0.22), and (0.21±0.20) cm; and the ventral and dorsal directions: (0.20±0.14), (0.17±0.18), and (0.16±0.17) cm, respectively. The translational set-up errors in the three directions of the integrated cervicothoracic immobilization device side group were better than those of the other two groups. Compared with the integrated cervicothoracic immobilization device side group, all the setup errors showed significant statistical differences (t=−9.85 to 5.89; all P<0.05), except for the thoracoabdominal flat frame side group in the Y direction (t=0.85, P>0.05). The three-dimensional displacement d values of the acromioclavicular joint in the three groups were (0.24±0.17), (0.28±0.16), and (0.23±0.13) cm, respectively. The difference of ΔY between thoracoabdominal flat frame elevation group and integrated cervicothoracic immobilization device side group was statistically significant ((0.11±0.11) cm vs. (0.13±0.11) cm, Z=−2.16, P<0.05). There were also significant differences in ΔZ ((0.18±0.15) cm vs. (0.12±0.10) cm, Z=−4.19, P<0.001) and the three-dimensional spatial displacement d values of the acromioclavicular joint ((0.28±0.16) cm vs. (0.23±0.13) cm, Z=−3.63, P<0.001) between the thoracoabdominal flat frame side and the integrated cervicothoracic immobilization device side groups.

Conclusion For mid-thoracic esophageal cancer patients with irradiated supraclavicular and infraclavicular region, shoulder immobilization using integrated cervicothoracic immobilization devices is better in translational set-up errors and three-dimensional spatial displacement of the acromioclavicular joint than thoracoabdominal flat frame, as it can effectively improve the accuracy of a radiotherapy plan.