Krueger Editha A, Schipper Matthew J, Koelling Todd, Marsh Robin B, Butler James B, Pierce Lori J
Department of Radiation Oncology, University of Michigan School of Medicine, Ann Arbor, MI, USA.
Int J Radiat Oncol Biol Phys. 2004 Nov 15;60(4):1195-203. doi: 10.1016/j.ijrobp.2004.04.026.
To compare the estimated radiation doses delivered to the cardiac chambers (CC) and coronary arteries (CA) for 5 postmastectomy radiotherapy (PMRT) techniques.
A dosimetry study of 20 left-sided PMRT cases was conducted. Cardiac chambers (left and right atria [LA/RA] and left and right ventricles [LV/RV]) and coronary vessels (left main [LM], left anterior descending [LAD], left circumflex [LCX], right coronary [RCA] and posterior descending [PDA] arteries) were contoured on contrast-enhanced CT scans and verified by a cardiologist (T.K.). Five PMRT techniques were applied to each case; 50 Gy in 2 Gy fractions was delivered to the chest wall +/- internal mammary node targets. The techniques were: (1) standard tangents (TAN); (2) cobalt (Co); (3) reverse hockey stick (RHS); (4) mixed photon/electron beam (20/80); and (5) partially wide tangent fields (PWTF). Three-dimensional dose calculations for 100 plans were performed for all structures. Plans were compared by using the mean dose (Dmean) and the volume that received more than 30 Gy (V(30)) and 45 Gy (V(45)) for each structure.
Cobalt and 20/80 techniques delivered higher Dmeans to the whole heart and individual cardiac chambers (RA, RV, LA, and LV) as compared with the other three techniques. The heart received a Dmean of 21.03 +/- 3.5 Gy from Co and 11.87 +/- 5.22 Gy from 20/80. The remaining techniques delivered heart Dmeans of 2.90-4.94 Gy. When V(30) was used as a metric, all techniques had comparably low V(30) to the heart, except for Co, which resulted in a significantly higher irradiated volume of right-sided cardiac chambers (59.06% +/- 30.7 for RA F-test < 0.0001; and 61.46% +/- 22.13 for RV, F-test < 0.0001). Dmean to the proximal LAD (LAD_p) was significantly higher for RHS (17.64 +/- 7.43 Gy) and 20/80 (20.52 +/- 8.36 Gy) and lowest for PWTF (9.5 +/- 4.16 Gy). The Dmean for the distal LAD (LAD_d) was significantly lower with PWTF (11.02 +/- 7.34 Gy) than with all other techniques, including TAN (p < 0.0001). Similar results for PWTF and TAN were observed when V30 and V45 were used.
Cardiac substructures receive the most radiation exposure after PMRT with CO, 20/80 or both and least exposure with PWTF. Although TAN resulted in significant sparing of the majority of the cardiac structures, a significantly higher dose and volume of LAD was exposed when compared with PWTF. Although the clinical relevance of these dose differences is not clearly understood, these dosimetric estimates can serve as a baseline in the development of new techniques for locoregional treatment that will further reduce cardiac exposure.
比较5种乳房切除术后放疗（PMRT）技术对心脏腔室（CC）和冠状动脉（CA）的估计辐射剂量。
对20例左侧PMRT病例进行了剂量学研究。在增强CT扫描上勾勒出心脏腔室（左、右心房[LA/RA]和左、右心室[LV/RV]）和冠状血管（左主干[LM]、左前降支[LAD]、左旋支[LCX]、右冠状动脉[RCA]和后降支[PDA]动脉），并由心脏病专家（T.K.）进行验证。对每个病例应用5种PMRT技术；以2Gy的分次剂量给予胸壁+/-内乳淋巴结靶区50Gy的照射。这些技术包括：（1）标准切线野（TAN）；（2）钴（Co）；（3）反向曲棍球棒野（RHS）；（4）混合光子/电子束（20/80）；（5）部分宽切线野（PWTF）。对所有结构进行了100个计划的三维剂量计算。通过使用平均剂量（Dmean）以及每个结构接受超过30Gy（V(30)）和45Gy（V(45)）的体积来比较各计划。
与其他三种技术相比，钴和20/80技术给予全心和各个心脏腔室（RA、RV、LA和LV）的Dmean更高。心脏从Co获得的Dmean为21.03±3.5Gy，从20/80获得的为11.87±5.22Gy。其余技术给予心脏的Dmean为2.90 - 4.94Gy。当以V(30)作为指标时，除Co外，所有技术对心脏的V(30)都相对较低，Co导致右侧心脏腔室的受照体积显著更高（RA为59.06%±30.7，F检验<0.0001；RV为61.46%±22.13，F检验<0.0001）。RHS（17.64±7.43Gy）和20/80（20.52±8.36Gy）对近端LAD（LAD_p）的Dmean显著高于PWTF（9.5±4.16Gy）。PWTF对远端LAD（LAD_d）的Dmean（11.02±7.34Gy）显著低于所有其他技术，包括TAN（p<0.0001）。当使用V30和V45时，PWTF和TAN得到了类似的结果。
在PMRT后，心脏亚结构接受Co、20/80或两者联合照射时的辐射暴露最多，而接受PWTF照射时最少。尽管TAN可使大多数心脏结构显著免受辐射，但与PWTF相比，LAD的剂量和体积显著更高。尽管这些剂量差异的临床相关性尚不清楚，但这些剂量学估计可作为进一步减少心脏暴露的局部区域治疗新技术开发的基线。
