宫颈癌术后盆腔调强放疗计划方法的剂量学比较研究

Dosimetric comparison between bone marrow-sparing intensity-modulated radiotherapy and conventional intensity-modulated radiotherapy for cervical cancer

目的比较两种调强放疗（IMRT）方法（对骨髓进行单独限量的BMS—IMRT，未对骨髓进行单独限量的IMRT）在宫颈癌靶体积剂量覆盖及危及器官保护方面的差异，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（町V），同时勾画小肠、直肠、膀胱、骨髓。进而设计出BMS—IMRT和IMRT的2种治疗计划，处方剂量为45Gy分25次，1．8Gy／次。所有计划都使95％靶区体积达到处方剂量要求。并用ADAC Pinnacle。计划系统提供的卷积或迭加算法对两种放疗技术的治疗计划进行剂量计算，比较靶区及危及器官剂量分布、剂量体积直方图参数。结果BMS—IMRT计划的靶区剂量均匀性不如IMRT，但其适形度优于IMRT计划，BMS—IMRT放疗计划中骨髓的V5、V10、V20、V30、V40分别比IMRT降低1．81％、8．61％、31．81％、29．50％、28．29％，而小肠、膀胱、直肠等危及器官的受量差别不大。结论对于宫颈癌术后患者BMS-IMRT降低了骨髓低剂量受照体积，从而有助于降低急性骨髓抑制发生概率、提高患者生活质量，值得在临床工作中推广应用。

Objective To compare bone marrow-sparing intensity-modulated radiotherapy （BMSIMRT） with conventional intensity-modulated radiotherapy （IMRT） without considering pelvic bone marrow （PBM） as a planning constraint in the treatment of cervical cancer after hysterectomy. Methods BMS-IMRT and IMRT planning were separately designed in a cohort of 10 patients with cervical cancer after hysterectomy. The prescribed dose was 95% planning target volume receiving 45 Gy/25 f. A commercially available TPS with convolution/superposition （CS） algorithm was used for dose calculation. Plans were compared according to dose-volume histogram （DVH） analysis in terms of PTV homogeneity （ HI）, conformity index （CI） as well as dose and volume parameters of organ at risks （OARs）. Results BMS-IMRT was better than IMRT in terms of CI, but inferior to the latter for HI. When compared with IMRT, V5 , Vl0, V20, V30 and V40 of PBM in BMS-IMRT were reduced by 1.81% ,8.61% ,31.81% ,29.50% and 28.29% , respectively. No statistically significant differences were found between BMS-IMRT and IMRT for dose distritutions of the small bowel, bladder or rectum. Conclusions For patients with cervical cancer after hysterectomy, BMS-IMRT can reduce the PBM volume irradiated by low dose, which may reduce acute hematologic toxicities.