宫颈癌术后盆腔螺旋断层调强和固定野调强技术的剂量学比较

Comparison of the Radiation Doses Used in Helical Tomotherapy and Fixed-field Intensity-modulated Radiotherapy for Cervical Cancer

目的比较对宫颈癌术后患者应用螺旋断层调强放疗(helical tomotherapy,HT)和固定野调强放疗(fixedfield intensity-modulated radiotherapy,FF-IMRT)两种计划方式进行放射治疗的剂量学差异。方法选择10例宫颈癌术后进行调强放疗的患者行CT模拟定位,勾画靶区及危及器官,对同一CT图像设计HT计划和FF-IMRT计划。评估靶区及危及器官的剂量分布。结果 HT计划组和FF-IMRT计划组靶区覆盖度均满足临床处方剂量要求。与FF-IMRT计划组相比,HT组的计划靶区(planning target volume,PTV)95%、PTV100%覆盖度增加,PTV105%覆盖度降低、Dmean及Dmax均明显降低(P=0.000),适形度指数和均匀性指数均优于FF-IMRT计划组(P=0.000)。与FF-IMRT计划组相比,HT计划组的膀胱V40降低约7%(P=0.000),Dmax平均值降低1.7 Gy(P=0.000);直肠V40降低约8%(P=0.000);小肠V30、V40分别降低4%、3%(P=0.002,P=0.000),Dmax平均值降低2 Gy(P=0.000);骨髓V30增加约5%(P=0.001),左右股骨头D5差异无统计学意义;马尾神经Dmax的平均值降低约2 Gy(P=0.030)。全身V20、V30、V40分别降低2%、1.3%、0.6%(P<0.01)。结论宫颈癌患者采用HT技术,靶区均匀性指数及适形度指数均较FF-IMRT技术明显提高,膀胱、直肠、小肠中高剂量区的体积进一步降低。HT技术在宫颈癌术后的临床应用中具有可行性,可作为一种新的照射方式推广。

Objective To compare the radiation doses appliedin helical tomotherapy （HT） and fixed- field intensity-modulated radiotherapy （FF-IMRT） for cervical cancer. Methods The computed tomography （CT） images of 10 patients with cervical cancer were transferred into the Eclipse planning system. HT and FF- IMRT plans were performed on a TomoTherapy treatment planning system （TPS） and an Eclipse TPS, respec- tively. Institutional dose-volume constraints used in cervical cancer were kept the same for both techniques. The targets and the organs-at-risk were evaluated. Results The coverage of HT planning group and FF-IMRT plan- ning group met the clinical requirements of the prescribed dose. Compared with the FF-IMRT planning group, planning target volume （PTV） 95% and PTV100% of HT planning group coverage increased, PTV105% be- came lower, Dmax and Dmean decreased, conformity index （CI） and homogeneity index （HI） improved （P = 0. 000）. Compared with the FF-IMRT planning group, V40 and Dmax of the bladder reduced by about 7% and 1.7 Gy, respectively （P =0. 000） ; V4o of the rectum reduced by about 8% （P =0. 000）, V3o and V40 of the small intestine reduced by 4% （P =0. 002） and 3% （P =0. 000）, Dmax reduced by 2 Gy （P =0. 000）, V3o of the bone marrow increased by 5% （P =0. 001 ） , D5 of the femoral heads showed no difference; Dmax of the cauda equine reduced by 2 Gy （P =0. 030） ; V2o, V3o, and V4o of the body reduced by 2%, 1.3%, 0. 6%, respectively （ P 〈 0. 01 ）. Conclusions HT has superior target HI and CI to the FF-IMRT in patients with cer- vical cancer, along with decreased high-dose regions in the bladder, rectum, and small intestine. Therefore, HT is feasible for the postoperative treatment of cervical cancer patients.