宫颈癌患者分次间位置不确定性对调强放疗靶区结构累积剂量的影响

Research on the effect of inter-fraction position uncertainty on target structure cumulative dose of intensity modulated radiotherapy in patients with cervical cancer

目的探讨分次间位置不确定性(IFPU)对宫颈癌靶区结构累积剂量(Dsum)与标准计划剂量(Dplan)比较,计算靶区百分剂量偏差(Ddev),为临床提供参考。方法选取2018-07-05-2019-12-27甘肃省肿瘤医院宫颈癌调强放疗(IMRT)患者110例,其中宫颈癌49例(仰卧位),宫颈癌术后61例(俯卧位)。处方剂量46.00~58.80 Gy,分割次数23~28次。运用锥形束计算机断层(CBCT)获取宫颈肿瘤IMRT IFPU,全程1 623次CBCT扫描。将IFPU输入治疗计划系统中,计算分次剂量并对其剂量叠加得到IFPU靶区结构Dsum,通过偏差公式计算获得靶区结构Ddev。IFPU采用单因素方差分析;Dsum与Dplan采用配对wilcoxon检验,配对用Dpair, D95%表示。结果 y轴宫颈癌仰卧位与俯卧位IFPU比较,差异有统计学意义,Z=-7.967,P<0.001。2种固定体位靶区结构Ddev比较,差异无统计学意义,临床靶区(CTV)all结构为例,D95%,dev,Z=-0.183,P=0.855。IFPU x、y、z轴组间比较,差异有统计学意义,F=3.734,P=0.024;两两比较,x与z轴比较,差异有统计学意义,均值差=-0.036,P=0.010;y与z轴比较,差异有统计学意义,均值差=-0.030,P=0.036。IFPU靶区结构Dsum和Dplan配对比较,差异均有统计学意义,均P<0.001。CTV2为0.13(-0.46,0.37),差异无统计学意义,Z=-0.314,P=0.753。IFPU靶区Dsum微分剂量体积直方图(DVH)呈负偏态分布,峰度降低。结论宫颈癌IMRT IFPU对靶区累积剂量影响存在统计学差异性,靶区累积剂量降低,靶区剂量均匀性变劣。宫颈癌患者IMRT治疗前需借助相应措施进行位置校准以保证靶区各结构剂量准确性。

Objective To compare the cumulative dose(Dsum) of cervical tumor target structure by iter-fractions position uncertainty(IFPU) with the standard planned dose(Dplan),and calcalate percentage dose deviation of target volume(Ddev) to provide clinical reference.Methods Totally 110 patients(49 cases of cervical cancer, supine position;61 cases of postoperative cervical cancer, prone position) with cervical tumor of IMRT in Gansu Cancer Hospital from July 5,2018 to 2019,December 27 were selected.The prescription dose was 46.00-58.80 Gy, 23-28 times.Use cone beam computed tomography(CBCT) were obtained IMRT IFPU of cervical tumor, total 1 623 times.The IFPU was inputted into the treatment planning system, and the fractionated dose was calculated and the dose was superimposed to get the IFPU target structure Dsum.The target structure Ddev was obtained by calculating the deviation formula.IFPU was analyzed by one-way ANOVA,Dsum and Dplan use paired Wilcoxon test(the pairing is represented by Dpair, D95%).Results Comparison of IFPU between supine position and prone position for cervical cancer, on the y-axis, the difference was statistically significant, Z=-7.967,P<0.001.There was no statistically significant difference in Ddev between all target volume in two fixed positions, CTVall,D95%,dev,Z=-0.183,P=0.855.Comparison between groups of x, y and z axes of IFPU,the difference was statistically significant, F=3.734,P=0.024.Pairwise comparison, the difference between x and z was statistically significant, mean difference=-0.036,P=0.010.The difference between y and z was statistically significant, mean difference=-0.030,P=0.036.Paired comparison of IFPU target structure Dsum with Dplan and Ddev,the difference was statistically significant, all P<0.001;the difference was not statistically significant, CTV2 was 0.13(-0.46,0.37),Z=-0.314,P=0.753.The IFPU target structure Dsum differential dose volume histogram(DVH)showed that negative skewness distribution and kurtosis was decreased.Conclusions The impact of IMRT IFPU on the cumulative dose of cervical cancer is statistically different,the cumulative dose in the target volume is reduced,it’s homogeneity index becomes worse.Before IMRT treatment of cervical tumors,corresponding measures need to be used to calibrate the position to ensure the accuracy of the dose of each structure in the target.