宫颈癌分段调强放射治疗计划的应用研究

The Applied Research of Phased Intensity-Modulated Radiotherapy for Cervical Cancer

目的探讨宫颈癌患者分段调强放射治疗(IMRT)中的靶区体积及危及器官(OAR)的受照范围和剂量变化。方法 33例宫颈癌患者(FIGO分期Ⅰb~Ⅲb期)行调强放射治疗和同步化疗,放射治疗前和放射治疗3周(30 Gy)后行第二次CT及MRI扫描,重新制定调强治疗后半程计划,采用6MV X线,7野调强照射技术(7f-IMRT);处方剂量均为50.4 Gy/28 F。应用剂量体积直方图(dose-volume histogram,DVH)比较分析分段计划时靶区及危及器官体积及剂量变化。结果治疗前、后半程计划处方剂量均较好地覆盖了靶区。平均96.7%的PTV接受处方剂量的照射。PTV平均剂量(5024±65.8)cGy;(4993±111.5)cGy,差异无统计学意义。治疗前后肿瘤靶体积(GTV)分别为(77.39±36.82)cm3、(52.01±30.6)cm3,GTV体积退缩(30.1±8.9)%;临床靶体积(CTV)分别是303.2~718.9 cm3、301.3~630.7cm3,体积退缩(7.7±1.1)%,前后差异均有统计学意义(P<0.05)。小肠35 Gy的平均体积是(35.0±15.0)%、(31.0±12.2)%;小肠40 Gy的平均体积是(27.0±12.0)%、(24.0±11.0)%,差异均有统计学意义(P<0.05)。而直肠、膀胱40 Gy的平均体积分别是(71.0±13.0)%、(70.0±11.0)%;(74.0±11.0)%、(69.0±9.0)%,差异无统计学意义。结论宫颈癌患者采用调强适形放射治疗技术能够产生理想的靶区剂量分布,分段计划有助于提高靶区的适形度,减少正常组织受照射的体积和剂量。

Objective To evaluate the volumetric and the dosimetric change of target volumes and organs at risk( OARs) during the course of intensity-modulated radiation therapy( IMRT) for cervical cancer. Methods 33 cases of cervical cancer( stage ⅠB ~ ⅢB) treated by concurrent chemotherapy and IMRT were included. CT and MR images were acquired for each patient before treatment and at 30 Gy during treatment. All treatment plans were prescribed to deliver 50. 4 Gy to the planning tumor volume( PTV) for seven-field( 7f-IMRT) using 6MV X-Ray. The target volumes and OARs were contoured based on the fused CT-MRI images by comparing the original plan and the second plan. Results 2 plans were good prescribed dose covering the target area. 96. 7% of the PTV accept the prescribed dose on average. PTV average dose was( 5024 ± 65. 8) cGy;( 4993 ±111. 5) cGy respectively. The tumor volume shrunk on average( 30. 1 ± 8. 9) % of the initial volume after treatment,tumor target volume( GTV) were( 77. 39 ± 36. 82) cm3;( 52.01 ±30.6) cm3; CTV respectively was303.2 ~718.9 cm3;301.3 ~630.74 cm3,volume shrank( 7. 7 ± 1. 1) %. 35 Gy average volume of small intestine was( 35. 0 ± 15. 0) %;( 31. 0 ± 12. 2) %. Average volume of 40 Gy of small intestine was( 27. 0 ± 12. 0) %;( 24. 0 ± 11. 0) % respectively. The difference was significant. 40 Gy average volume of Rectum and bladder were( 71. 0 ± 13. 0) %;( 74. 0 ± 11. 0) % respectively and compared to( 70. 0 ± 11. 0) %;( 69.0 ±9.0) % respectively. There were no significant dosimetric differences in OARS. Conclusion Cervical cancer patients with intensity modulated radiotherapy technology can produce the ideal target area dose distribution,phased program helps to improve the target form degrees,reduce the volume of irradiated normal tissue and dose.