三种放疗技术对早期鼻咽癌颈部皮肤设定限制剂量差异研究

目的 比较固定野dIMRT、VMAT和HT技术在早期鼻咽癌放疗过程中颈部皮肤受量情况。方法 选取 16例完成放疗的早期鼻咽癌病例,将颈部外轮廓内缩3 mm生成皮肤。分别以传统方式(TP组)和将颈部皮肤作为OAR (NP组)进行剂量限制设计计划。统计各组计划中颈部皮肤 Dmean、V5—V70。对同一放疗技术的两组计划行配对t检验;对3种放疗技术的同一处理方法三组行方差分析。结果 HT组皮肤 Dmean、V5、V10、V30—V70均高于dIMRT和VMAT组(P=0.00、0.00、0.00、0.00、0.00、0.00、0.00、0.02)。dIMRT技术NP组皮肤 Dmean、V10—V60较TP组分别降低7%、8%、22%、25%、38%、59%、85%(P=0.00、0.00、0.00、0.00、0.00、0.00、0.00);VMAT技术NP组皮肤 Dmean、V20—V40较TP组分别降低4%、19%、29%、34%(P=0.02、0.01、0.02、0.01);HT技术NP组皮 肤V30—V70较TP组分别降低20%、29%、50%、67%、100%(P=0.00、0.00、0.00、0.00、0.03)。结论 早期鼻咽癌放疗计划设计中HT较dIMRT和VMAT引起的颈部皮肤受量高,dIMRT和VMAT结果近似;在进行早期鼻咽癌计划设计时将颈部皮肤作为OAR进行剂量限制可明显降低颈部皮肤受量。

Neck skin dose planning for early-stage nasopharyngeal carcinoma:a comparative study of three radiotherapy methods

Objective To compare the neck skin dose between fixed-field dynamic intensity-modulated radiation therapy (dIMRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) in the treatment of early-stage nasopharyngeal carcinoma. Methods A total of 16 early-stage nasopharyngeal carcinoma patients undergoing radiotherapy were enrolled as subjects. The neck skin was delineated by contraction of the outer edge of neck by 3 mm. Dose planning was made by the traditional method (TP group) and a new method (NP group), in which the neck skin was considered as the organ at risk. Dmean and V5-V70 for the neck skin were recorded. The paired t-test was used to analyze the differences between two plans in each radiotherapy method. An analysis of variance was used to compare the same plan between the three radiotherapy Methods. Results The HT group had significantly higher Dmean and V5-V70 for the neck skin than the dIMRT group and the VMAT group (P=0.00,0.00,0.00,0.00,0.00,0.00,0.00,0.02). Using dIMRT, the Dmean and V10-V60 for the neck skin were reduced by 7%, 8%, 22%, 25%, 38%, 59%, and 85% in the NP group than in the TP group (P=0.00,0.00,0.00,0.00,0.00,0.00,0.00). Using VMAT, the Dmean and V20-V40 for the neck skin were reduced by 4%, 19%, 29%, and 34% in the NP group than in the TP group (P=0.02,0.01,0.02,0.01). Using HT, the V30-V60 for the neck skin were reduced by 20%, 29%, 50%, and 67% in the NP group than in the TP group (P=0.00,0.00,0.00,0.00,0.03). Conclusions In the treatment of early-stage nasopharyngeal carcinoma, HT causes a higher radiation dose to the neck skin than dIMRT and VMAT, while dIMRT and VMAT have similar neck skin doses. The neck skin dose can be significantly reduced with the neck skin as the organ at risk.