左乳腺癌保乳术后全乳和锁骨上下及内乳淋巴结区三种放疗方式的剂量学研究

目的:对左乳腺癌保乳术后全乳及锁骨上下、内乳淋巴结引流区三种放疗方式在靶区及危及器官(organs at risk,OARs)的剂量学进行研究。方法:选取2018年1月至2019年10月20例于昆明医科大学第一附属医院行左乳腺癌保乳术后放疗患者的定位CT资料,设计固定野滑窗调强放疗(dynamic multi-leaf collimator,dMLC)、容积弧形调强放疗(volumetric intensity modulated arctherapy,VMAT)和螺旋断层放疗(tomotherapy,HT)三种计划,并对剂量指标进行统计学分析。结果:HT在术后瘤床(plan target volume of tumor bed,PTVtb)的平均剂量(mean dose,Dmean)、D1、适形度(homogeneity index,HI)和全乳及淋巴引流区的计划靶区(plan target volume,PTV)的Dmean、均匀性(conformity index,CI)均优于dMLC和VMAT,并且降低心脏和患侧肺的Dmean、V5、V10、V30。HT在冠状动脉左前降支和右冠状动脉的Dmean以及D1比较中剂量最低,但相比VMAT及dMLC,HT增加健侧乳腺的D1和Dmean。结论:对左乳腺癌保乳术后患者,HT对降低心脏毒性和保护患侧肺最有优势,但对健侧肺低剂量控制不如VMAT和dMLC,dMLC对健侧肺及健侧乳腺低剂量控制最佳,但对心脏及患侧肺的高剂量控制最差。在临床中需根据实际情况选择合适的计划方式。

Dosimetric study of three different irradiation methods of treating left breast cancer with total breast and clavicle and internal breast lymph node area after breast conservative surgery

  Objective  To evaluate the differences in dosimetry distribution among three different radiotherapy methods used for the treatment of left breast cancer affecting the total breast, clavicle, and internal breast lymphatic drainage area after breast-conserving surgery. The target coverage and organs at risk (OARs) in each method were compared.  Methods  Twenty breast cancer patients who were treated at First Affiliated Hospital of Kunming Medical College, from January 2018 to October 2019 were selected. All patients underwent left-side breast conserving postoperative radiotherapy. Dynamic multi-leaf collimator (dMLC), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) plans were designed for each patient. We compared and analyzed the parameters of planning target volume of the tumor bed (PTV_tb), planning target volume (PTV), and OARs according to these plans using a paired t-test.  Results  The mean dose (D_mean), D₁, homogeneity index (HI) of PTV_tb, D_mean, and conformity index (CI) of the PTV of the HT plan were better than those of the DMLC and VMAT plans. The D_mean, V₅, V₁₀, and V₃₀ of the heart and lungs were significantly decreased in the HT plan. The HT plan had the lowest D_mean and D₁ values for the left anterior descending coronary artery and right coronary artery. However, compared with the VMAT and DMLC plans, the HT plan had increased values for D₁ and D_mean of the right breast.  Conclusion  For patients with left breast cancer who have undergone breast conserving surgery, HT can reduce the dose to the ipsilateral lung and heart. However, the low-dose area of the contralateral lung was larger with the HT plan than with the VMAT and dMLC plans. With the dMLC plan, the dose to the contralateral lung was the lowest, but the doses to the ipsilateral lung and heart were higher than those with the VMAT and HT plans. An appropriate treatment plan should be chosen according to the condition of the patient.