Abstract：Objective To obtain the inter-fractional set-up errors of intensity-modulated radiotherapy (IMRT) of cervical cancer by cone-beam CT (CBCT), and to analyze the variations of the set-up errors on the cumulative dose deviation of the target volume. Methods A total of 48 patients with cervical cancer who underwent IMRT were enrolled in this study, and the set-up errors of 696 CBCTs were obtained. The set-up errors were input into the treatment planning system, and the cumulative set-up error dose was obtained by superposing the set-up errors dose. The deviation percentage was calculated by the deviation formula and the standard planning dose. Results The set-up errors caused the offset of isocenter distance by 0.58(0.36,0.80) cm. Different statistical differences were noted between the cumulative set-up error dose and the standard planning dose by WilCoxon test. All the dose deviations in the target volume were reduced, and the differential dose volume histogram (DVH) appeared negatively skewed, and the peak value was declined. The DVH diagram shifted to the left with an inverse S-curve and the slope was increased. The HIdeviation of the target volume from small to large were:CTV1,CTV2,GTV/CTV,CTV3,CTVn,CTVall,and GTVnd;The HIdeviation of the target volume were increased. Conclusions The effect of set-up errors in IMRT of cervical cancer upon the cumulative doses of the target volume significantly differs. The cumulative dose of the target volume is reduced, and the uniformity of the target volume dose becomes worse. The uncertainty of the inter-fractional position leads to an increase or decrease in the the fractional doses of the target volume. The biological effect on tumor cells and the tumor recurrence remains to be investigated. In IMRT of cervical cancer, the CBCT position calibration is required before each treatment to ensure the dose accuracy of each structure in the target volume.
Ouyang Shuigen,Tao Na,Liu Tingting et al. Effect of inter-fractional positional uncertainty on cumulative dose of target volume in intensity-modulated radiotherapy of cervical cancer[J]. Chinese Journal of Radiation Oncology, 2021, 30(8): 822-827.
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