乳腺癌术后放疗降低心脏照射剂量的新方法--心脏前壁区域作为独立的危及器官

摘要

Objective To investigate the feasibility of anterior myocardial territory(AMT) as an independent organ at risk(OAR) in postoperative intensity modulated radiotherapy(IMRT) for left-sided breast cancer patients who received breast conserved surgery(BCS) to avoid unnecessary cardiac radiation. Methods The archived computed tomographic(CT) scans of 23 patients who received adjuvant radiotherapy were selected randomly for this dosimetric study. The same radiation oncologist delineated the clinical target volume(CTV) and OARs including both lungs, the right breast, the heart, left ventricle(LV), AMT and the same physicist designed two IMRT plans including IMRT(H+LV) and H(AMT) plan. The prescribed dose(PD) was 50Gy with 25 fractions. For the planning target volume(PTV) and OARs, the various dose-volume histogram(DVH) parameters were compared with paired t-test. Results For the PTV, the homogeneity index, conformity index, and coverage index of both IMRT plans were not different statistically. Compared with IMRT(AMT), The maximal dose to AMT increased significantly and mean dose to AMT increased without statistical difference(P =0.069), the V12Gy, V13Gy, V15Gy, V17Gy and V20Gy increased 15.37%, 18.87%, 26.48%, 27.11% and 26.04% respectively(P <0.05), and the V5Gy, V7Gy, V8Gy and V10Gy of LV did 4.21%、16.72%、20.91%and 19.14%(P <0.05). All the dose-volume parameters of the heart and LV as well as majority of the dose-volume parameters of right lung and breast were not different statistically. Conclusion For left-sided breast patients with breast conserved surgery,anterior myocardial territory replaced the heart as an independent OAR may decrease the cardiac dose in the postoperative radiotherapy.%　　目的探索心脏前壁区域(anterior myocardial territory，AMT)作为独立的危及器官在左乳腺癌保乳术后放疗中心脏保护的可行性。方法随机选取23例左乳癌接受保乳术后及术后辅助放疗的患者的计划CT图像。由同一个放疗医师勾画靶区和危及器官(OAR)，OAR包括心脏(H)、AMT、左心室(left ventricle, LV)、左右肺和右侧乳腺。每个患者由物理师设计两个调强治疗计划(IMRT)，一个是以AMT作为目标函数，另一个是以H+LV作为目标函数。所有治疗计划的处方剂量均为50Gy，25次。比较计划靶区(PTV)、AMT、LV、心脏、左右肺和右侧乳腺的剂量体积参数。结果 IMRT(AMT)和IMRT(H+LV)2个计划的PTV剂量的均匀指数、适形指数、覆盖指数均无明显差别。与IMRT(AMT)计划相比，IMRT(H+LV)中AMT的最大剂量明显增加，平均剂量增加有统计学意义，AMT的V12Gy、V13Gy、V15Gy、V17Gy和V20Gy分别增加15.37%、18.87%、26.48%、27.11%(P <0.05)，LV的V5Gy、V7Gy、V8Gy和V10Gy分别增加4.21%、16.72%、20.91%和19.14%(P <0.05)。心脏和左肺的各个剂量体积参数无统计学差别，多数右肺和右乳腺的剂量体积参数无明显统计学差别。结论在左乳腺癌术后放疗中，AMT可作为替代心脏的一个独立危及器官可明显降低心脏照射剂量。