宫颈癌术后盆腔三种放射治疗计划设计方法的剂量学研究

Dosimetric Comparison of Bone Marrow-Sparing Intensity-Modulated Radiotherapy Versus Conventional Intensity-Modulatedr Radiotherapy for Treatment of Cervical Cancer

目的:比较对骨髓进行单独限量的调强放疗(BMS-IMR)、三维适形放疗(3DCRT)、常规放疗(CRT)方法在宫颈癌靶体积剂量覆盖及危及器官(OAR)保护方面的差异,探讨宫颈癌患者术后盆腔外照射骨髓保护的合理方法。方法:对10例宫颈癌术后患者进行模拟CT增强扫描,在计划系统内勾画临床靶体积(CTV),CTV均匀外扩1.0cm生成计划靶体积(PTV),同时勾画小肠、直肠、膀胱、骨髓作为OAR。进而设计出BMS-IMR、3DCRT、CRT3种治疗计划,处方剂量为45Gy/1.8Gy/25次。所有计划都使95%靶区体积达到处方剂量要求。比较靶区及危及器官的剂量分布、剂量-体积直方图(DVH)中的多个指标。结果:BMS-IMRT计划的靶区剂量均匀性不如3DCRT和CRT,但其适形度明显优于后两者。与3DCRT相比,BMS-IMRT放疗计划降低了骨髓、小肠、膀胱、直肠的受照剂量。与CRT相比,BMS-IMRT降低了30Gy～40Gy范围内骨盆骨髓(PBM)的受照体积,但却增加了5Gy～20Gy范围内PBM的受照体积;另外,BMS-IMRT还降低了小肠、膀胱、直肠在几乎所有剂量范围内的受照体积。结论:与3DCRT相比,BMS-IMRT降低了骨髓的受照体积;而与CRT相比,BMS-IMRT降低了骨髓在高剂量范围内的受照体积。因此,对于宫颈癌术后患者,BMS-IMRT可降低发生急性骨髓抑制的几率,提高病人的生活质量,值得在临床工作中推广应用。

Objective： To compare bone marrow-sparing intensity-modulated radiotherapy （BMS-IMRT） with conventional （four-field box [3DCRT] and anteroposterior-posteroanterior [CRT]） techniques in the treatment of cervical cancer. Methods： For a cohort of 10 patients, BMS-IMRT, 3DCRT and CRT planning were designed. The prescribed dose was 45Gy/1.8Gy/25f, 95% of the planning target volume received this dose. Doses were computed with a commercially available TPS. Plans were compared according to dose-volume histogram （DVH） analysis in terms of PTV homogeneity and conformity indices （HI and CI） as well as OARs dose and volume parameters. Results： BMS-IMRT had an advantages over 3DCRT and CRT in terms of CI, but inferior to the latter two for HI. BMS-IMRT was superior to 3DCRT in reducing the dose to PBM, small bowel, bladder and rectum. Compared with CRT, BMS-IMRT reduced the volume irradiated to the doses from 30Gy to 40Gy, but increased the volume irradiated to the low doses from 5 Gy to 20 Gy. In addition, BMS-IMRT reduced the volume of small bowel, blad- der, rectum at nearly all dose levels. Conclusion： BMS-IMRT reduced irradiation of PBM compared with 3DCRT technique. Compared with CRT technique, BMS-IMRT reduced the volume of PBM irradiated to high doses. Therefore, for patients with cervical cancer after hysterectomy, BMS-IMRT might reduce acute hematologic toxicity （HT） compared with conventional techniques.