Setup error of Orfit versus vacuum bag in radiotherapy for cervical cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective To compare the setup errors of the negative pressure vacuum air cushion (vacuum bag) and the Orfit body foam fixator (Orfit frame) in radiotherapy for cervical cancer.Methods A total of 40 patients receiving three-dimensional radiotherapy for cervical cancer were enrolled in this study and equally and randomly divided into vacuum bag group and Orfit frame group.And the two groups were divided into Orfit-1 group, Orfit-2 group, vacuum-1 group, and vacuum-2 group according to the treatment course.The Orfit-1 group and vacuum-1 group were the data in the first 12 treatments, while the Orfit-2 group and vacuum-2 group were the data in the following 13 treatments.A cone-beam computed tomography scan was performed before each treatment to analyze setup error and then the body position was corrected to start the treatment.Comparison of continuous data between groups was made by paired t-test, while comparison of categorical data was made by chi-square test.Results There was a significant difference in the setup error in y-axis direction between the Orfit-1 group and the Orfit-2 group (P=0.003) and the setup error in r-axis direction between the vacuum-1 group and the vacuum-2 group (P=0.013).There were no significant differences in the setup errors in four directions (x-axis, y-axis, z-axis, and r-axis) between the Orfit-1 group and the vacuum-1 group (P>0.05).There were significant differences in the setup errors in y-axis and z-axis directions between the Orfit-2 group and the vacuum-2 group (P=0.007;P=0.001).Conclusions The Orfit frame and the vacuum bag have their own advantages and disadvantages in the fixation of body position in radiotherapy for cervical cancer.The setup error can be improved by long vacuum bags, ultrasound bladder capacity scanner, image-guided radiotherapy, or sectional radiotherapy plan.