Department of Radiation Oncology, Shandong Cancer Hospital, Jinan, PR China.
Technol Cancer Res Treat. 2011 Oct;10(5):487-94. doi: 10.7785/tcrt.2012.500225.
The purpose of this study is to compare the characteristics of 3D-conformal radiotherapy (3D-CRT), fixed-field intensity-modulated radiotherapy (IMRT) and RapidArc for esophageal squamous cell carcinoma (ESCC) treated with elective nodal irradiation (ENI). CT datasets of 20 patients with ESCC were included and plans for single and double arcs of RapidArc (RA1 and RA2), 7-field IMRT and 3D-CRT were created and optimized for each patient. The goal was to deliver 59.6 Gy to ≥95% of the planning target volume (40 Gy to electively irradiated lymph nodal regions) while meeting the same normal-tissue dose constraints. The plans were compared based on dosimetric characteristics of target and organs at risk (OARs), monitor units (MUs), and appraised beam-on time. Both RA2 and IMRT resulted in similar target coverage (V95%, 97.84±1.50% for RA2 versus 96.96±1.15% for IMRT), homogeneity index (HI, 0.11±0.02 for RA2 versus 0.10±0.01 for IMRT) and conformity index (CI, 0.81±0.03 for RA2 versus 0.79±0.04 for IMRT), which displayed slightly better than single arc (V95%=94.55±1.50%, HI=0.12±0.02, CI=0.80±0.02) and much better than 3D-CRT (V95%=91.17±2.89%, HI=0.15±0.03, CI=0.60±0.07). The total lung V20, V30 was reduced approximately from 31%, 16% (3D-CRT) to 22%, 13% (IMRT) and 20%, 12% (RA2); the heart V30, V40 from 29%, 21% (3D-CRT) to 28%, 20% (IMRT) and 27%, 18% (RA2). The maximum dose to the spinal cord was 44.26±2.60 Gy for 3D-CRT, 42.47±2.40 Gy for IMRT, and 42.79±1.81 Gy for RA2. The number of MUs per fraction reduced from 990±165 (IMRT) to 503±70 (3D-CRT) and 502±79 (RA2). Appraised beam-on time of RapidArc was 1.2-2.4 min, which was lower than IMRT with 5.4 min by average. RapidArc, especially for double arcs plan could provide slight improvements in OARs sparing and lower MUs without compromised target qualities compared with IMRT, which was much better than 3D-CRT for ESCC treated with ENI.
本研究旨在比较三维适形放疗（3D-CRT）、固定野调强放疗（IMRT）和适形调强放疗（RapidArc）在治疗食管鳞状细胞癌（ESCC）伴预防性淋巴结照射（ENI）中的特点。纳入 20 例 ESCC 患者的 CT 数据集，为每位患者分别创建并优化了单弧和双弧 RapidArc（RA1 和 RA2）、7 野 IMRT 和 3D-CRT 计划。目标是在满足相同的正常组织剂量限制的情况下，将 59.6Gy 传递至计划靶区（PTV）的≥95%（40Gy 至选择性照射的淋巴结区域）。基于靶区和危及器官（OARs）、监测器单位（MUs）和射束开启时间的剂量学特征比较了这些计划。双弧 RA2 和 IMRT 均导致相似的靶区覆盖率（V95%，RA2 为 97.84±1.50%，IMRT 为 96.96±1.15%）、均匀性指数（HI，RA2 为 0.11±0.02，IMRT 为 0.10±0.01）和适形指数（CI，RA2 为 0.81±0.03，IMRT 为 0.79±0.04），其显示出略优于单弧（V95%=94.55±1.50%，HI=0.12±0.02，CI=0.80±0.02）和明显优于 3D-CRT（V95%=91.17±2.89%，HI=0.15±0.03，CI=0.60±0.07）。全肺 V20、V30 分别降低约 31%、16%（3D-CRT）至 22%、13%（IMRT）和 20%、12%（RA2）；心脏 V30、V40 分别降低约 29%、21%（3D-CRT）至 28%、20%（IMRT）和 27%、18%（RA2）。脊髓最大剂量为 3D-CRT 为 44.26±2.60Gy，IMRT 为 42.47±2.40Gy，RA2 为 42.79±1.81Gy。每个射野的 MU 数从 990±165（IMRT）减少到 503±70（3D-CRT）和 502±79（RA2）。RapidArc 的评估射束开启时间为 1.2-2.4min，平均比 IMRT 的 5.4min 低。与 IMRT 相比，RapidArc 尤其是双弧计划可在不降低靶区质量的情况下，略微改善 OAR 保护和降低 MU，而 3D-CRT 则对 ESCC 伴预防性淋巴结照射的效果较差。
