title: Comparison of whole-field simultaneous integrated boost VMAT and IMRT in the treatment of nasopharyngeal cancer.
abstract: To study the feasibility of using volumetric-modulated arc therapy (VMAT) to deliver whole-field simultaneous integrated boost (WF-SIB) to treat patients with nasopharyngeal cancer (NPC). WF-SIB intensity-modulated radiotherapy (IMRT) plans, one-arc WF-SIB VMAT plans, and two-arc WF-SIB VMAT plans were generated with identical objective functions for 8 patients with NPC of various stages. Isodose distributions and dose-volume histograms were evaluated. Dosimetric and biological quality indices of clinical target volume (CTV) and organs at risk (OARs) were calculated to study the optimization capability of these 3 modalities in the treatment of patients with NPC. The optimization time, delivery time, required monitor units (MUs), and delivery accuracy were also compared to investigate the feasibility of these 3 modalities. There was no significant difference (p = 0.92) in target coverage (TC) between WF-SIB IMRT (99.00 ± 0.79) and two-arc WF-SIB VMAT (97.98 ± 1.29). However, both had higher TC than one-arc VMAT plans (89.92 ± 6.32, p < 0.01). IMRT demonstrated the best protection of the spinal cord, whereas two-arc VMAT showed the minimum Dmax to OARs. No other significant differences were observed among these 3 modalities on CTV coverage and OAR sparing. The delivery and MU efficiency of one-arc and two-arc WF-SIB VMAT were greatly improved compared with WF-SIB IMRT. The optimization time of one-arc and two-arc WF-SIB VMAT plans were 5 and 10 times greater than that of WF-SIB IMRT, respectively. The delivery accuracy of WF-SIB VMAT was not affected by the increased freedom. For patients with NPC, one-arc WF-SIB VMAT might not be able to achieve sufficient TC, whereas two-arc WF-SIB VMAT was able to achieve reasonable TC. No significant advantage on OAR protection was demonstrated by VMAT compared with IMRT. WF-SIB VMAT has significantly shorter delivery times, but WF-SIB IMRT may still be the first treatment choice for patients with NPC.
authors: Radiotherapy and Chemotherapy Department, The 1st Affiliated Hospital of Wenzhou Medical College, Wenzhou, China.
authors: Xiance
authors: X
authors: Jin
authors: Jinling
authors: J
authors: Yi
authors: Yongqiang
authors: Y
authors: Zhou
authors: Huawei
authors: H
authors: Yan
authors: Ce
authors: C
authors: Han
authors: Congying
authors: C
authors: Xie
mesh_terms: D005240:Feasibility Studies; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D011446:Prospective Studies; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
keywords: IMRT; Nasopharyngeal cancer; Simultaneous integrated boost; VMAT; Whole field