Ⅱ期和Ⅲ期直肠癌术后盆腔调强放疗两种计划比较研究

Dosimetric comparison of postoperative intensity-modulated radiotherapy for stage Ⅱ - Ⅲ rectal cancer

目的通过对Ⅱ、Ⅲ期直肠癌术后盆腔调强放疗（IMRT）两种计划比较，探讨保护骨髓最佳方案和提高同期放化疗可行性。方法选取15例Ⅱ、Ⅲ期直肠癌术后患者经增强cT模拟定位后，在计划系统中勾画靶体积。设计对骨髓单独限量和不限量两种计划，在规定计划靶体积至少达95％处方剂量前提下比较靶区剂量分布及小肠、膀胱、骨髓受量体积并配对￡检验差异。结果骨髓单独限量计划靶区适形度（CI值）优于骨髓不限量的（1．06：1．04，t=-2．61，P=0．023），但剂量均匀性（HI值）差于骨髓未限量的（0．81：0．75，t=-2．34，P=0．037）。骨髓单独限量计划的骨髓接受低剂量照射体积（V；、V10、V20、V30、V40）小于骨髓未限量的（97．09％：98．72％，t=-2．34，P=0．037；92．38％：96．46％，t=-2．41，P=0．033；83．36％：91．70％，t=-3．18，P=0．008；51．47％：69．65％，t=-4．92，P=0．000；36．34％：49．57％，t=-2．66，P=0．021），小肠和膀胱大都相似，只有膀胱V20不同（77．32％：92．39％，t=-3．52，P=0．004）。结论骨髓单独限量计划显著降低了骨髓低剂量受照体积，在一定程度上降低急性骨髓抑制发生率，增强了同期放化疗在Ⅱ、Ⅲ期直肠癌患者可行性。

Objective To explore the optimal method of protecting bone marrow in postoperative concurrent chemoradiotherapy of stage Ⅱ - Ⅲ rectal cancer by comparing two techniques of intensity- modulated radiotherapy （IMRT）. Methods Fifteen patients with stage Ⅱ - Ⅲ rectal cancer after surgery had CT simulation. Clinical target volume, small bowel, bladder and bone marrow were contoured. Two IMRT treatment plannings with and without bone marrow-sparing （ BMS-IMRT and IMRT） were separately designed. The dose distribution was compared based on that 95% of the planning target volume received the prescribed dose. Results BMS-IMRT had an advantage over IMRT in terms of conformity indices （ 1.06： 1.04,t = -2. 61 ,P =0. 023）, but inferior to IMRT for homogeneity indices （0. 81： 0. 75 ,t = -2. 34,P= 0.037））. Compared with IMRT, BMS-IMRT reduced the Vs, V10, V20, V30, V40 of bone marrow （97. 09% ： 98. 72% , t= -2.34, P = 0. 037 ; 92. 38% ： 96. 46% , t= -2.41, P=0.033;83.36%： 91.70%, t= -3. 18, P=0.008;51.47%：69.65%, t= -4.92, P=0.000;36.34%：49.57%, t= -2. 66, P = 0. 021 ）. The doses received by small bowel and bladder were similar between BMS-IMRT and IMRT, except that the V2o of bladder was lower in BMS-IMRT （77.32% ： 92. 39% , t = - 3.52, P = 0. 004）. Conclusions BMS-IMRT reduces low dose volume of bone marrow without increasing dose to other risk organs. BMS-IMRT might reduce acute hematologic toxicity and increase the feasibility of postoperative concurrent chemoradiotherapy in stage Ⅱ - Ⅲ rectal cancer.