Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Department of Diagnostic Radiology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Pract Radiat Oncol. 2022 Nov-Dec;12(6):487-495. doi: 10.1016/j.prro.2022.02.008. Epub 2022 Mar 2.
To map the locations of level I axilla (Ax-L1) lymph nodes (LNs), evaluate the clinical target volume (CTV) coverage defined by the Radiation Therapy Oncology Group (RTOG) Breast Cancer Atlas, and assess the optimal techniques for whole-breast and Ax-L1 irradiation (WBI + Ax-L1).
We identified 76 patients newly diagnosed with breast cancer with 1 to 4 positive LNs confirmed by axillary dissection. The locations of 116 involved Ax-L1 LNs on diagnostic computed tomography (CT) were mapped onto simulated CT images of a standard patient. Ax-L1 LN coverage by the RTOG atlas was evaluated, and a modified Ax-L1 CTV with better coverage was proposed. Treatment plans were designed for WBI + Ax-L1 with high tangential simplified intensity modulated radiation therapy (HT-sIMRT) and volumetric modulated arc therapy (VMAT) and for WBI + RTOG Ax-L1 with VMAT with a prescription dose of 50 Gy in 25 fractions, respectively. The differences in dosimetric parameters were compared.
The RTOG Atlas missed 29.3% of LNs. Modification by extending 1 cm caudal and 0.5 cm anterior to the RTOG-defined CTV borders allowed the modified Ax-L1 CTV to encompass 90.5% of LNs. All plans met the required prescription dose to WBI and Ax-L1. The mean dose and the V20 and V5 (percentage volume receiving 20 Gy and 5 Gy) of the ipsilateral lung were 11.7 Gy, 23.0%, and 38.1% for HT-sIMRT WBI + Ax-L1 and 8.9 Gy, 16.4%, and 32.5% for VMAT WBI + Ax-L1 plans, respectively. The mean heart doses in the left-sided plans were 3.2 Gy and 3.0 Gy, respectively. The V30 of the humeral head and the minimum dose to the axillary-lateral thoracic vessel junction were 2.0% versus 1.8% and 45.5 Gy versus 45.7 Gy for VMAT WBI + Ax-L1 and VMAT WBI + RTOG Ax-L1 plans, respectively.
A modified Ax-L1 CTV with expansion of the caudal and anterior borders might provide better coverage. Compared with HT-sIMRT WBI + Ax-L1, VMAT WBI + Ax-L1 provided an adequate dose to the Ax-L1 while decreasing the doses to most normal tissues. Coverage of the modified Ax-L1 did not increase the dose to organs at risk compared with coverage of RTOG Ax-L1.
描绘Ⅰ区腋窝（Ax-L1）淋巴结（LNs）的位置，评估放射治疗肿瘤学组（RTOG）乳腺癌图谱定义的临床靶区（CTV）覆盖范围，并评估全乳和 Ax-L1 照射（WBI+Ax-L1）的最佳技术。
我们确定了 76 例新诊断为乳腺癌的患者，这些患者的腋窝清扫术证实有 1 至 4 个阳性 LNs。在模拟标准患者的 CT 图像上对诊断 CT 上 116 个受累 Ax-L1 LN 的位置进行了定位。评估了 RTOG 图谱中 Ax-L1 LN 的覆盖范围，并提出了一种覆盖范围更好的改良 Ax-L1 CTV。分别为 WBI+Ax-L1 设计了高切线简化调强放疗（HT-sIMRT）和容积调强弧形治疗（VMAT）的治疗计划，以及为 WBI+RTOG Ax-L1 设计了 VMAT 治疗计划，处方剂量为 50 Gy，25 个分数。比较了剂量学参数的差异。
RTOG 图谱漏诊了 29.3%的 LNs。通过将 RTOG 定义的 CTV 边界向尾侧和前侧扩展 1 cm 和 0.5 cm，可以使改良的 Ax-L1 CTV 包含 90.5%的 LNs。所有计划均满足 WBI 和 Ax-L1 的规定剂量要求。同侧肺的平均剂量和 V20 和 V5（接受 20 Gy 和 5 Gy 的体积百分比）分别为 HT-sIMRT WBI+Ax-L1 为 11.7 Gy、23.0%和 38.1%，VMAT WBI+Ax-L1 计划分别为 8.9 Gy、16.4%和 32.5%。左侧计划的平均心脏剂量分别为 3.2 Gy 和 3.0 Gy。肱骨头的 V30 和腋外侧胸血管交界处的最小剂量分别为 VMAT WBI+Ax-L1 为 2.0%和 45.5 Gy，VMAT WBI+RTOG Ax-L1 为 1.8%和 45.7 Gy。
扩大尾侧和前侧边界的改良 Ax-L1 CTV 可能会提供更好的覆盖范围。与 HT-sIMRT WBI+Ax-L1 相比，VMAT WBI+Ax-L1 为 Ax-L1 提供了足够的剂量，同时降低了大多数正常组织的剂量。与 RTOG Ax-L1 相比，改良 Ax-L1 的覆盖范围不会增加对危险器官的剂量。
