左侧乳腺癌改良根治术后胸壁和内乳区三维适形和调强放疗计划剂量学研究

Dosimetric Study on Three-dimensional Conformal Radiotherapy and Intensity-modulated Radiotherapy for Left Breast Cancer Patients Receiving Postmastectomy Radiotherapy Including Chest wall and Internal Mammary Nodes

目的:通过比较常规混合射线计划、部分扩大切线野计划、分段切线野计划和调强计划在靶区覆盖率和正常组织剂量的差异,为临床选择放射治疗计划提供参考。方法:30例左侧乳腺癌患者均接受CT扫描,在CT图像上勾画胸壁、内乳区、心脏、同侧肺和对侧乳腺,每例患者均设计3种不同的三维适形放射治疗计划比较,选择最优的三维适形放射治疗计划和调强计划比较。结果:3种三维适形放射治疗计划比较,对于总计划靶区(PTV),3种治疗计划的覆盖率都是令人满意的。对于内乳区PTV,分段切线野计划(V47.5:95.19±3.90%)、部分扩大切线野计划(V47.5:96.83%±4.56%)与常规混合射线计划(V47.5:88.16±7.77%)相比,剂量更均匀;常规混合射线计划内乳区PTV的高剂量区VD105%、VD110%、VD115%和VD120%都明显多于其他两种放射治疗计划。对于心脏和肺,分段切线野计划(心脏8.47±2.30Gy,肺12.20±2.20Gy)与部分扩大切线野计划(心脏11.97±3.54Gy,肺13.39±1.97Gy)、常规混合射线计划(心脏11.18±2.53Gy,肺13.17±2.03Gy)相比,降低了心脏的平均剂量和同侧肺的平均剂量。将分段切线野计划和调强计划比较,对于总PTV,两种治疗计划的覆盖率都是令人满意的。内乳区PTV的高剂量区VD105%、VD110%、VD115%和VD120%两种计划间差异无统计学意义(P>0.05),两种计划的高剂量区都较小。调强放射治疗计划(CI:0.64±0.02)的靶区适形性优于分段切线野计划(CI:0.45±0.02)。但调强放射治疗计划(心脏:19.03±3.48Gy;肺:15.58±2.01Gy)心脏和同侧肺的平均剂量高于分段切线野计划(心脏:8.47±2.30Gy;肺:12.20±2.20Gy),还使得心脏和同侧肺的V5-10较大。对侧乳腺,2种计划的平均剂量无显著差异(分段切线野技术1.00±0.02Gy,调强放射治疗技术1.08±0.25Gy)。结论:分段切线野计划较好地平衡了靶区覆盖完整性和保护正常组织,对于左侧乳腺癌改良根治术后胸壁和内乳区照射患者有一定剂量学优势。

Objective：Three three-dimensional conformal radiotherapy（3D-CRT） techniques,namely,standard tangents,partially wide tangents（PWT）,and partition techniques plus intensity modulated radiotherapy（IMRT） technique have been used to radiate the chest wall（CW） and internal mammary nodes（IMN） following mastectomy for left-breast cancer patients.Dosimetric comparisons have been made in terms of dose homogeneity within planning target volume（PTV） and dose to critical structures.Methods： Thirty patients underwent CT simulation,while CW,IMN,left lung,heart and contralateral breast were contoured.The best technique of the three 3D-CRT was then compared with IMRT.Results： All three 3D-CRT techniques provided satisfactory coverage regarding total PTV.The PWT and the Partition gave better coverage of IMN PTV with V47.5 of 96.83%±4.56% and 95.19%±3.90% compared to Standard Tangents（88.16±7.77%）,P0.05.The Standard Tangents also contributed the biggest IMN VD105%,VD110%,VD115% and VD120%.The lowest mean dose of the heart and lung were achieved by the Partition（heart 8.47±2.30 Gy,lung 12.20±2.20 Gy）,compared with PWT（heart 11.97±3.54Gy,lung 13.39±1.97Gy） and Standard Tangents（heart 11.18±2.53Gy,lung 13.17±2.03Gy）.Compare IMRT with the Partition,both techniques provided satisfactory coverage.VD105%、VD110%、VD115%和VD120% of the IMN PTV with Partition were not significantly different from those of IMRT（P0.05）.The conformity indexes（CI） with IMRT（CI：0.64±0.02） were better than those with the Partition（CI：0.45±0.02）.The mean dose,V5,V10 and V5~10 of heart and left lung with the Partition were significantly lower than those with the IMRT.The mean dose of contralateral breast with the Partition was not significantly different from the IMRT（Partition 1.00±0.02Gy,IMRT 1.08±0.25Gy）.Conclusions： The partition technique may provide homogeneous target coverage while maintaining low doses to normal tissue.