State Key Laboratory of Oncology in Southern China, Department of Radiation Oncology, Sun Yat-sen University Cancer Centre, Guangzhou, China.
PLoS One. 2013 Sep 25;8(9):e75304. doi: 10.1371/journal.pone.0075304. eCollection 2013.
To compare volumetric modulated arc therapy (VMAT) with conventional step and shoot intensity modulated radiation therapy (s-IMRT) in nasopharyngeal carcinoma (NPC) patients, and identify which T category patient gains the maximum benefit from VMAT.
Fifty-two patients that randomly selected from 205 patients received VMAT at a single center were retrospectively replanned with s-IMRT. For a fair comparison, the planning target volume (PTV) coverage of the 2 plans was normalized to the same level. A standard planning constraint set was used; the constraints for the organs at risk (OARs) were individually adapted. The calculated doses to the PTV and OARs were compared for s-IMRT and VMAT plans generated using the Monaco treatment planning system.
VMAT and s-IMRT plans had similar PTV coverage and OAR sparing within all T categories. However, in stratified analysis, VMAT plans lead to better or similar sparing of the OARs in early T category patients; and lead to poorer sparing of the OARs in advanced T category patients (P<0.05). VMAT shows significant advantages for low dose burden (P<0.05) compared with s-IMRT. The delivery time per fraction for VMAT (424±64 s) was shorter than s-IMRT (778 ± 126 s, p<0.01).
VMAT provides similar dose coverage of the PTVs and similar/better normal tissue sparing in early T category NPC, and poorer OARs sparing in advanced T category NPC. And VMAT shows significant advantages for low dose burden and delivery time.
比较容积旋转调强放疗（VMAT）与常规的分步照射强度调制放疗（s-IMRT）在鼻咽癌（NPC）患者中的应用，并确定哪种类别患者从 VMAT 中获益最大。
本研究回顾性地选择了 205 例接受单中心 VMAT 治疗的患者中的 52 例，并用 s-IMRT 进行重新计划。为了进行公平比较，将两种方案的计划靶区（PTV）覆盖范围归一化为相同水平。使用标准的计划约束集，对危及器官（OAR）的约束条件进行个体化调整。使用 Monaco 治疗计划系统比较了 s-IMRT 和 VMAT 计划计算得到的 PTV 和 OAR 剂量。
VMAT 和 s-IMRT 计划在所有 T 类别中均具有相似的 PTV 覆盖范围和 OAR 保护。然而，在分层分析中，VMAT 计划在早期 T 类别患者中能更好或相似地保护 OAR；而在晚期 T 类别患者中，VMAT 计划则导致 OAR 保护较差（P<0.05）。与 s-IMRT 相比，VMAT 具有显著的低剂量负担优势（P<0.05）。VMAT 每分次的治疗时间（424±64 s）短于 s-IMRT（778 ± 126 s，p<0.01）。
VMAT 为早期 T 类别 NPC 患者提供了相似的 PTV 剂量覆盖和相似/更好的正常组织保护，而在晚期 T 类别 NPC 中，OAR 保护较差。VMAT 具有显著的低剂量负担和治疗时间优势。
