Brief Article
Copyright ©2012 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Oct 7, 2012; 18(37): 5266-5275
Published online Oct 7, 2012. doi: 10.3748/wjg.v18.i37.5266
Volumetric-modulated arc therapy vs c-IMRT in esophageal cancer: A treatment planning comparison
Li Yin, Hao Wu, Jian Gong, Jian-Hao Geng, Fan Jiang, An-Hui Shi, Rong Yu, Yong-Heng Li, Shu-Kui Han, Bo Xu, Guang-Ying Zhu
Li Yin, Hao Wu, Jian Gong, Jian-Hao Geng, Fan Jiang, An-Hui Shi, Rong Yu, Yong-Heng Li, Shu-Kui Han, Bo Xu, Guang-Ying Zhu, Department of Radiotherapy, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
Author contributions: Yin L took charge of the whole work, carried out data collection, performed treatment planning and drafted the manuscript; Wu H, Gong J, Jiang F, Han SK and Xu B performed physics checkups and plan evaluation; Shi AH, Yu R and Li YH determined the patient accrual and radiation field; Zhu GY, Xu B and Han SK provided mentorship for this work; Wu H and Geng JH revised the manuscript; Zhu GY designed the study and approved the final version to be published; and all authors have read and approved the final manuscript.
Supported by The National Natural Science Foundation of China, No. 30870738
Correspondence to: Guang-Ying Zhu, MD, PhD, Department of Radiotherapy, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China. zgypu@yahoo.com.cn
Telephone: +86-10-88196120 Fax: +86-10-88196120
Received: February 25, 2012
Revised: June 27, 2012
Accepted: July 9, 2012
Published online: October 7, 2012
Abstract

AIM: To compare the volumetric-modulated arc therapy (VMAT) plans with conventional sliding window intensity-modulated radiotherapy (c-IMRT) plans in esophageal cancer (EC).

METHODS: Twenty patients with EC were selected, including 5 cases located in the cervical, the upper, the middle and the lower thorax, respectively. Five plans were generated with the eclipse planning system: three using c-IMRT with 5 fields (5F), 7 fields (7F) and 9 fields (9F), and two using VMAT with a single arc (1A) and double arcs (2A). The treatment plans were designed to deliver a dose of 60 Gy to the planning target volume (PTV) with the same constrains in a 2.0 Gy daily fraction, 5 d a week. Plans were normalized to 95% of the PTV that received 100% of the prescribed dose. We examined the dose-volume histogram parameters of PTV and the organs at risk (OAR) such as lungs, spinal cord and heart. Monitor units (MU) and normal tissue complication probability (NTCP) of OAR were also reported.

RESULTS: Both c-IMRT and VMAT plans resulted in abundant dose coverage of PTV for EC of different locations. The dose conformity to PTV was improved as the number of field in c-IMRT or rotating arc in VMAT was increased. The doses to PTV and OAR in VMAT plans were not statistically different in comparison with c-IMRT plans, with the following exceptions: in cervical and upper thoracic EC, the conformity index (CI) was higher in VMAT (1A 0.78 and 2A 0.8) than in c-IMRT (5F 0.62, 7F 0.66 and 9F 0.73) and homogeneity was slightly better in c-IMRT (7F 1.09 and 9F 1.07) than in VMAT (1A 1.1 and 2A 1.09). Lung V30 was lower in VMAT (1A 12.52 and 2A 12.29) than in c-IMRT (7F 14.35 and 9F 14.81). The humeral head doses were significantly increased in VMAT as against c-IMRT. In the middle and lower thoracic EC, CI in VMAT (1A 0.76 and 2A 0.74) was higher than in c-IMRT (5F 0.63 Gy and 7F 0.67 Gy), and homogeneity was almost similar between VMAT and c-IMRT. V20 (2A 21.49 Gy vs 7F 24.59 Gy and 9F 24.16 Gy) and V30 (2A 9.73 Gy vs 5F 12.61 Gy, 7F 11.5 Gy and 9F 11.37 Gy) of lungs in VMAT were lower than in c-IMRT, but low doses to lungs (V5 and V10) were increased. V30 (1A 48.12 Gy vs 5F 59.2 Gy, 7F 58.59 Gy and 9F 57.2 Gy), V40 and V50 of heart in VMAT was lower than in c-IMRT. MUs in VMAT plans were significantly reduced in comparison with c-IMRT, maximum doses to the spinal cord and mean doses of lungs were similar between the two techniques. NTCP of spinal cord was 0 for all cases. NTCP of lungs and heart in VMAT were lower than in c-IMRT. The advantage of VMAT plan was enhanced by doubling the arc.

CONCLUSION: Compared with c-IMRT, VMAT, especially the 2A, slightly improves the OAR dose sparing, such as lungs and heart, and reduces NTCP and MU with a better PTV coverage.

Keywords: Esophageal cancer; Treatment planning; Intensity modulated radiotherapy; Volumetric modulated arc radiotherapy; Normal tissue complication probability