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Objective: To explore the effects of cone beam CT (CBCT)-guided radiotherapy set-up errors on irradiation dose of patients with upper and middle esophageal cancer. Methods: A total of 60 patients with middle and upper esophageal cancer admitted to our hospital from May 2017 to May 2019 were selected as the research subjects. All patients underwent CBCT images and planned CT image acquisition. CBCT scan was performed on patients before radiotherapy, and the CBCT image was matched with the planned CT image to obtain linear errors in three directions of left-right (x-axis), head-to-foot (y-axis) and front-to-back (z-axis), and the errors and distribution of errors were analyzed. The simulated actual irradiation system was used to carry out a simulation plan to obtain the actual irradiation target area and the irradiation dose of normal tissues, and compared it with the pre-treatment plan, and the effects of set-up errors on irradiation dose of patients were studied. Results: The overall set-up error of patients was (2.91± 2.20) mm in x-axis, (3.89± 2.17) mm in y-axis and (2.44± 1.64) mm in z-axis, and the MPTV of x-axis was 4.054 mm, and MPTV of y-axis was 8.183 mm and MPTV of z-axis was 3.482 mm. The Dmin, Dmean and D95% of CI and PTV of the simulation plan were significantly lower than those of the standard plan (all P<0.05), and the HI of simulation plan was lower than that of standard plan (P<0.05). The spinal cord Dmax of simulation plan was higher than that of standard plan (P<0.05), and there were no significant differences in the lung V20 and Dmean and heart V40 between standard plan and simulation plan (all P>0.05). Conclusions: CBCT-guided radiotherapy set-up errors have little effects on patients with upper and middle esophageal cancer. It improves the PTV irradiation dose and the treatment accuracy, and has a protective effect on spinal cord. Set-up errors have no significant effects on the dose distribution of the heart and lung. [ABSTRACT FROM AUTHOR]

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