宫颈癌限定盆骨的全盆调强放疗骨髓受照的剂量学研究

Dosimetry of bone marrow irradiated by intensity modulated whole pelvis radiotherapy for cervical cancer

目的评价应用限定盆骨骨髓的全盆调强放疗（intensity modulated whole pelvis radiotherapy，IM—WPRT）减少骨髓受照体积和剂量的可能性。方法15例局部进展期宫颈癌患者，增强CT模拟定位，勾画CTV、刚及危险器官直肠、膀胱、小肠、股骨头和包括第5腰椎和骶椎的全盆骨。CTV包括宫颈癌原发灶、子宫、宫旁组织以及区域淋巴结。CTV外扩1．0cm为刚。设计对限定和不限定盆骨骨髓的IM—WPRT，95％PTV=50Gy／25f，比较两种IM—WPRT计划的PTV、盆骨骨髓及其他危险器官的DVH及剂量分布。结果加骨髓限值的IM—WPRT比不加限值的IM—WPRT在不同剂量水平均明显减少骨髓的受照体积，尤其在20～50Gy差异有显著统计学意义（P≤0．008）；在80％和100％的处方剂量时，前者较后者分别减少6．5％和8．8％的骨髓体积。在低剂量水平10～30Gy（P≤0．025）和10～20Gy（P≤0．008）分别对左、右股骨头有明显的保护作用。同时，限定骨髓的IM—WPRT未影响PTV的剂量覆盖率和剂量均匀性。结论限定骨髓的IM—WPRT可以明显减少骨髓的受照剂量和体积，并减少股骨头的受照体积。证实限定盆骨骨髓的IM—WPRT计划是可行的，为降低同步放化疗治疗进展期宫颈癌血液毒性提供了剂量学依据。

Objective To assess the effect of applying intensity modulated whole pelvis radiotherapy（ IM- WPRT） on reducing the irradiated volume of pelvic bone marrow （BM）. Methods 15 consecutive patients with cervical cancer underwent IM-WPRT. The clinical target volume（CTV） and the planning target volume （PTV = CTV ＋ 1.0 cm） and pelvic BM were contoured. Two plans were created for each patient： an IM-WPRT treatment plan （excluding pelvic BM）, and a pelvic BM-sparing （BMS） IM-WPRT plan. Dose-volume histograms for the PTV and critical organs were evaluated. Results BMS IM-WPRT treatment plans demonstrated a significant reduction of the volume of pelvic BM at various dose levels, especially at 20-50 Gy（ P ≤0.008）. Compared with the conventional IM-WPRT, BMS IM-WPRT decreased the BM volume by 6.5% and 8.8% at 80% and 100% of the prescription dose, respectively. Furthermore, the BMS IM-WPRT plans,with adequate coverage and the same dose homogeneity of PTV, resulted in significant sparing of other critical organs. Conclusions BMS IM- WPRT is superior to pelvic BM. It provides dosimetric evidence of reducing hematologic toxicity of concurrent radiochemotherapy in locally advanced cervical cancer.