title: Radiation therapy for nasopharyngeal carcinoma using simultaneously integrated boost (SIB) protocol: a comparison planning study between intensity modulated arc radiotherapy vs. intensity modulated radiotherapy.
abstract: The aim of this paper is to compare the dosimetric difference between intensity-modulated arc therapy (IMAT) and conventional intensity-modulated radiation therapy (IMRT) for radiotherapy of nasopharyngeal carcinoma (NPC) using simultaneously integrated boost (SIB) protocol. Ten patients with nasopharyngeal carcinoma underwent SIB protocol were retrospectively studied. The plan target volume (PTV) of NPC contained nasopharynx gross target volume and the positive neck lymph nodes, PTV1 contained the high-risk sites of microscopic extension and the whole nasopharynx and PTV2 contained the low-risk sites. The prescription dose of PTV was 66 Gy/30 fractions, and for PTV1 60 Gy/30 fractions and for PTV2 54 Gy/30 fractions. IMAT (two 358° arcs) and IMRT (7 fields) plans were designed for each patients using SIB strategies. The monitor unit (MU), treatment time (T) and dosimetric difference between IMRT and IMAT were compared. IMAT can achieve better conformal index (CI) than IMRT (P < 0.05) for all PTVs, while no significant difference were found in homogeneity index (HI) (P > 0.05). There's no significant difference found in radiation dose of brain stem, lenses and parotids, while the maximum dose of spinal cord of IMAT was higher than IMRT (P < 0.05). The monitor unit of IMRT (1308 ± 213) was more than IMAT (606 ± 96) (P < 0.05), while the treatment time of IMRT (540 ± 160S) was more than IMAT (160 ± 10S). This study shows that IMAT using SIB strategies for NPC radiotherapy can achieve similar target coverage with better conformity with less MU and delivery time comparing to IMRT.
authors.affiliation: Department of Radiation Oncology, Shandong Cancer Hospital, Shandong Provincial Key Laboratory of Radiation Oncology, Shandong Academy of Medical Sciences, Jinan, PR China.
authors.forename: Tonghai
authors.initials: T
authors.lastname: Liu
authors.forename: Jinhu
authors.initials: J
authors.lastname: Chen
authors.forename: Guanzhong
authors.initials: G
authors.lastname: Gong
authors.forename: Guifang
authors.initials: G
authors.lastname: Zhang
authors.forename: Tong
authors.initials: T
authors.lastname: Bai
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.forename: Changsheng
authors.initials: C
authors.lastname: Ma
authors.forename: Yong
authors.initials: Y
authors.lastname: Yin
mesh_terms: D002277:Carcinoma / Q000473:pathology / Q000532:radiotherapy*; D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012189:Retrospective Studies; D012984:Software; D047368:Tumor Burden