Heart-protected Role of Left Ventricle as Organ at Risk in Postoperative Intensity Modulation Radiotherapy for Left-sided Breast Cancer with Breast-conserving Operation
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摘要: 目的 探索左心室(left ventricle，LV)作为新的危及器官(organ at risk，OAR)在左乳腺癌保乳术后放疗中心脏保护的作用。方法随机选取13例左乳腺癌接受保乳术及术后辅助放疗患者的计划CT图像。由同一个放疗医师勾画靶区和OAR ，OAR包括心脏、LV、左右肺和右侧乳腺。每个患者由物理师制定4个治疗计划。所有治疗计划的处方剂量均为50 Gy ，25次。比较PTV、心脏、左右肺和右侧乳腺的剂量体积参数。结果与TF计划相比，在IMRT计划中PTV的最大剂量［除了IMRT(H)计划外］和最小剂量有不同程度增加。与IMRT(H)计划相比，在IMRT(H+LV)和IMRT(LV)计划中PTV内的最大剂量分别增加，大于V110 高剂量体积增加。与TF计划相比，在IMRT计划中心脏的平均剂量、中位剂量、V5、V10 分别增加0.9%~22.3% (P>0.05)、78.3%~110.6%(P<0.05)、179.3%~209.2%(P<0.05)、24.7%~97.7%。心脏最大剂量、V15、V20分别降低18.6%~36.7%(P<0.05)、7.2%~52.6%、48.3%~79.5%(P<0.05)。左肺在IMRT计划中高剂量体积（大于V17）明显降低，而低剂量体积（小于V12）明显升高。结论左乳腺癌保乳术后IMRT中增加左心室作为OAR可降低心脏照射剂量。Abstract: Objective To study the role the left ventricle (LV) as a novel organ at risk (OAR) in postoperative intensity modulated radiotherapy (IMRT) for left-sided breast cancer patients who received breast conserved surgery (BCS) to protect the heart from unnecessary radiation. Methods The archived computed tomographic (CT) scans of 13 patients who received adjuvant radiotherapy (RT) in our department were selected at random for this dosimetric study.The same radiation oncologist contoured the clinical target volume (CTV) and OARs including lungs，the right breast，the heart and left ventricle (LV) and the same physicist did one tangential field (TF) pan and 3 IMRT plans.The prescribed dose (PD) was 50 Gy with 25 fractions.For the planning target volume (PTV) and OARs，the various dose-volume histogram (DVH) parameters were compared. Results Compared with TF plan，the maximal ［except for the IMRT (H)］and minimal doses increased differently.And Compared with IMRT(H) plan，the maximal dose and the volume higher than 110% of prescribed dose increased.Compared with TF plan，the mean heart dose，the median dose，V5，V10 increased 0.9%~22.3% (P>0.05),78.3%~110.6%(P<0.05),179.3%~209.2%(P<0.05),24.7%~97.7% respectively in all the IMRT plans.The maximal dose，V15，V20 decreased 18.6%~36.7% (P<0.05),7.2%~52.6%,48.3%~79.5%(P<0.05) respectively.For left lung，the high dose volume (>V17) decreased and the low dose volume (
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