Department of Oncology, Xiangya Hospital, Central South University, No. 87, Xiangya Road, Changsha, Hunan Province 410008, China.
Biomed Res Int. 2018 Jun 4;2018:2653497. doi: 10.1155/2018/2653497. eCollection 2018.
To compare the dosimetric differences between volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) in treating early T-stage nasopharyngeal carcinoma (NPC).
Ten patients with early T-stage NPC who received tomotherapy using simultaneously integrated boost (SIB) strategies were replanned with VMAT (RapidArc of Varian, dual-arc). Dosimetric comparisons between the RapidArc plan and the HT plan included the following: (1) D98, homogeneity, and conformity of PTVs; (2) sparing of organs at risk (OARs); (3) delivery time and monitor units (MUs).
(1) Compared with RapidArc, HT achieved better dose conformity (CI of PGTVnx + nd: 0.861 versus 0.818, = 0.004). (2) In terms of OAR protection, RapidArc exhibited significant superiority in sparing ipsilateral optic nerve (Dmax: 27.5Gy versus 49.1Gy, < 0.001; D2: 23.5Gy versus 48.2Gy, < 0.001), contralateral optic nerve (Dmax: 30.4Gy versus 49.2Gy, < 0.001; D2: 26.2Gy versus 48.1Gy, < 0.001), and optic chiasm (Dmax: 32.8Gy versus 48.3Gy, < 0.001; D2: 30Gy versus 47.6Gy, < 0.001). HT demonstrated a superior ability to protect the brain stem (D1cc: 43.0Gy versus 45.2Gy, = 0.012), ipsilateral temporal lobe (Dmax 64.5Gy versus 66.4 Gy, = 0.015), contralateral temporal lobe (Dmax: 62.8Gy versus 65.1Gy, = 0.001), ipsilateral lens (Dmax: 4.27Gy versus 5.24Gy, = 0.009; D2: 4.00Gy versus 5.05Gy, = 0.002; Dmean: 2.99Gy versus 4.31Gy, < 0.001), contralateral lens (Dmax: 4.25Gy versus 5.09Gy, = 0.047; D2: 3.91Gy versus 4.92Gy, = 0.005; Dmean: 2.91Gy versus 4.18Gy, < 0.001), ipsilateral parotid (Dmean: 36.4Gy versus 41.1Gy, = 0.002; V30Gy: 54.8% versus 70.4%, = 0.009), and contralateral parotid (Dmean: 33.4Gy versus 39.1Gy, < 0.001; V30Gy: 48.2% versus 67.3%, = 0.005). There were no statistically significant differences in spinal cord or pituitary protection between the RapidArc plan and the HT plan. (3) RapidArc achieved a much shorter delivery time (3.8 min versus 7.5 min, < 0.001) and a lower MU (618MUs versus 5646MUs, < 0.001).
Our results show that RapidArc and HT are comparable in D98, dose homogeneity, and protection of the spinal cord and pituitary gland. RapidArc performs better in shortening delivery time, lowering MUs, and sparing the optic nerve and optic chiasm. HT is superior in dose conformity and protection of the brain stem, temporal lobe, lens, and parotid.
比较容积调强弧形治疗（VMAT）和螺旋断层放疗（HT）在治疗早期 T 期鼻咽癌（NPC）中的剂量学差异。
10 例采用同时整合boost（SIB）策略行 HT 治疗的早期 T 期 NPC 患者，采用 VMAT（瓦里安的 RapidArc，双弧）重新计划。RapidArc 计划与 HT 计划的剂量学比较包括以下方面：（1）PTVs 的 D98、均匀性和适形性；（2）危及器官（OARs）的保护；（3）治疗时间和监测单位（MUs）。
（1）与 RapidArc 相比，HT 实现了更好的剂量适形性（PGTVnx + nd 的 CI：0.861 与 0.818， = 0.004）。（2）在保护 OAR 方面，RapidArc 在保护同侧视神经（Dmax：27.5Gy 与 49.1Gy， < 0.001；D2：23.5Gy 与 48.2Gy， < 0.001）、对侧视神经（Dmax：30.4Gy 与 49.2Gy， < 0.001；D2：26.2Gy 与 48.1Gy， < 0.001）和视交叉（Dmax：32.8Gy 与 48.3Gy， < 0.001；D2：30Gy 与 47.6Gy， < 0.001）方面具有显著优势。HT 显示出更好的保护脑干（D1cc：43.0Gy 与 45.2Gy， = 0.012）、同侧颞叶（Dmax 64.5Gy 与 66.4 Gy， = 0.015）、对侧颞叶（Dmax：62.8Gy 与 65.1Gy， = 0.001）、同侧晶状体（Dmax：4.27Gy 与 5.24Gy， = 0.009；D2：4.00Gy 与 5.05Gy， = 0.002；Dmean：2.99Gy 与 4.31Gy， < 0.001）、对侧晶状体（Dmax：4.25Gy 与 5.09Gy， = 0.047；D2：3.91Gy 与 4.92Gy， = 0.005；Dmean：2.91Gy 与 4.18Gy， < 0.001）、同侧腮腺（Dmean：36.4Gy 与 41.1Gy， = 0.002；V30Gy：54.8% 与 70.4%， = 0.009）和对侧腮腺（Dmean：33.4Gy 与 39.1Gy， < 0.001；V30Gy：48.2% 与 67.3%， = 0.005）的能力。RapidArc 计划和 HT 计划在脊髓和垂体保护方面没有统计学显著差异。（3）RapidArc 实现了更短的治疗时间（3.8 分钟与 7.5 分钟， < 0.001）和更低的 MU（618MUs 与 5646MUs， < 0.001）。
我们的结果表明，RapidArc 和 HT 在 D98、剂量均匀性和脊髓、垂体保护方面相当。RapidArc 在缩短治疗时间、降低 MU 和保护视神经和视交叉方面表现更好。HT 在剂量适形性和保护脑干、颞叶、晶状体和腮腺方面更具优势。
