宫颈癌复发放疗中不同照射方式的剂量学研究

Dosimetry study of different irradiation technologies for patients with recurrence of cervical cancer

目的针对宫颈癌复发病例,比较逆向调强（IMRT）、三维适形（3D-CRT）及超级伽玛刀弧形适形（SGS-CRT）三种照射方式的剂量学特点。方法对15例宫颈癌复发患者进行IMRT、3D-CRT及SGS-CRT计划设计,以包绕计划靶区（PTV）体积95%的等剂量线为处方剂量线,分别给予50Gy的处方剂量,分次方案均为2Gy×25次,根据剂量-体积直方图（DVH）评价三种照射方式中靶区和危及器官的剂量学特点。结果 3D-CRT的95%处方剂量包括靶区体积（99.9%±0.2%）高于IMRT（99.5%±0.5%）及SGS-CRT（99.3%±0.8%,P〈0.05）;SGS-CRT的靶区剂量梯度（85%±20%）明显高于IMRT（10%±7%）及3D-CRT（8%±5%,P〈0.05）;IMRT的适形指数（0.9±0.3）优于SGS-CRT（0.8±0.2,P〈0.05）,且SGS-CRT优于3D-CRT（0.7±0.5,P〈0.05）。DVH显示,在1030Gy之间,SGS-CRT膀胱平均受照体积（27.8%）明显低于IMRT（40.1%）和3D-CRT（57.4%,P〈0.05）;在545Gy之间,直肠平均受照射体积SGS-CRT（25.4%）明显低于IMRT（48.9%）和3D-CRT（73.2%,P〈0.05）;在小肠剂量分布上,三种照射方式无显著差异。结论在宫颈癌复发放疗中,SGS-CRT具有一定剂量学优势,值得在临床应用中进一步探讨。

Objective To compare the dosimetric characteristics of intensity-modulated radiation therapy（IMRT）,three-dimensional conformal radiation therapy（3D-CRT） and super gamma knife arc conformal radiotherapy（SGS-CRT） for patients with recurrence of cervical cancer.Methods Treatment planning of IMRT,3D-CRT and SGS-CRT for 15 patients with recurrence of cervical cancer was designed,and the prescription dose（50Gy,2.0Gy×25） covered 95% of the planning target volume（PTV）.The dosimetric characteristics of the 3 irradiation technologies in target region and organs at risk were compared by analyzing dose-volume histogram（DVH）.Results The target volume of 95% prescription dose was significantly higher in 3D-CRT（99.9%±0.2%） than in IMRT（99.5%±0.5%） and SGS-CRT（99.3%±0.8%,P〈0.05）;the dose gradient of target region was significantly higher in SGS-CRT（85%±20%） than in IMRT（10%±7%） and 3D-CRT（8%±5%,P〈0.05）;the conformal index of target region was higher in IMRT（0.9±0.3） than in SGS-CRT（0.8±0.2,P〈0.05）,and the latter was higher than that in 3D-CRT（0.7±0.5,P〈0.05）.The DVH showed that the radiation volumes of bladder was lower in SGS-CRT（27.8%） than in IMRT（40.1%） and 3D-CRT（57.4%,P〈0.05） when the dosage ranged from 10 to 30 Gy,and the radiation volumes of rectum was lower in SGS-CRT（25.4%） than in IMRT（48.9%） and 3D-CRT（73.2%,P〈0.05） when the dosage ranged from 5 to 45 Gy,while there was no significant difference among the 3 irradiation technologies of the radiation volumes of small bowel.Conclusion SGS-CRT shows some dosimetric advantages in treating patients with recurrence of cervical cancer.