乳房保留术后野中野正向调强全乳房照射的腋窝淋巴结剂量学研究

Radiation doses to axillary lymph nodes in patients with early breast cancer receiving field-in-field forward-planned intensity-modulated radiotherapy for whole breast irradiation after breast-conserving surgery

目的 研究早期乳腺癌患者保乳术后采用野中野正向调强技术进行单纯乳房照射时各站腋窝淋巴结剂量分布及影响因素.方法 37例乳腺癌患者保乳术后采用“野中野”技术照射乳房,在定位CT图像上勾画患侧第Ⅰ、Ⅱ、Ⅲ站和胸肌间淋巴结靶区,并勾画腋静脉,在三维放疗计划软件上逐站分析其所接受的剂量.配对t检验分析影响腋窝淋巴结剂量分布的因素.结果 在全乳PTV处方剂量50 Gy分25次情况下,第Ⅰ、Ⅱ、Ⅲ站和胸肌间淋巴结被95％处方剂量所包括体积比平均值分别为34.7％、6.1％、0.4％和39.6％,Dmean分别为30.8、15.7、5.0Gy和28.8 Gy;腋静脉以下和以上淋巴结区域被95％处方剂量包括的体积比为45.6％和0.7％,Dmean为38.2 Gy和6.7 Gy.乳房照射野的上界距离肱骨头的距离是影响腋静脉以下淋巴结区域Dmean的唯一有意义因素（P=0.037）.结论 全乳正向调强野中野技术对腋静脉以下腋窝淋巴结的实际照射剂量是不可忽略的,必须在分析保乳术后腋窝淋巴结控制率时予以考虑.

Objective To evaluate the radiation doses to the axillary lymph nodes in patients with early breast cancer receiving field-in-field forward-planned intensity-modulated radiotherapy （FIF-FP-IMRT） for whole breast irradiation after breast-conserving surgery,and to analyze the factors influencing the doses to the axillary lymph nodes.Methods Thirty-seven patients with breast cancer treated by breast-conserving surgery were evaluated.All patients received FIF-FP-IMRT for whole breast irradiation （not involving regional lymph nodes）.Delineation of axillary levels Ⅰ-Ⅲ,interpectoral lymph nodes,and axillary vein was made on CT images,and a dosimetric analysis was made using 3D treatment planning software.The influential factors for the dose distribution in axillary lymph nodes were analyzed by paired t-test.Results The mean percent volumes receiving at least 95％ of the prescribed dose （50 Gy/25 fractions for whole breast PTV）（V95） for axillary levels Ⅰ,Ⅱ,and Ⅲ and interpectoral lymph nodes were 34.7％,6.1％,0.4％,and 39.6％,respectively,and the mean doses to axillary levels Ⅰ,Ⅱ,Ⅲ and interpectoral lymph nodes were 30.8 Gy,15.7 Gy,5.0 Gy,and 28.8 Gy,respectively.The mean V95 values for the lymph node areas below and above the axillary vein were 45.6％ and 0.7％,respectively,and the mean doses were 38.2 Gy and 6.7 Gy,respectively.The distance between the upper border of the radiation field and the humeral head was the only significant factor influencing the mean dose to the lymph node area below the axillary vein （P =0.037）.Conclusions In FIF-FP-IMRT for whole breast irradiation,the actual dose delivered to the axillary lymph nodes below the axillary vein cannot be neglected and should be taken into consideration when analyzing the local control of the axillary lymph nodes after breast-conserving surgery.