Comparison of Two Different IMRT Planning Techniques in the Treatment of Nasopharyngeal Carcinoma. Effect on Parotid Gland Radiation Doses

Overview

Journal Strahlenther Onkol

Specialties Oncology
Radiology

Date 2013 Jun 11

PMID 23748231

Citations 10

Authors

E K Uzel

S Karacam

O Elicin

O Uzel

Affiliations

Soon will be listed here.

Abstract

Purpose: To compare the effect of two different intensity-modulated radiation therapy (IMRT) planning techniques on parotid gland doses in patients with nasopharyngeal carcinoma (NPC).

Patients And Methods: Radiotherapy for 10 NPC patients referred to the University of Istanbul Cerrahpasa Medical School was planned with arc- and static seven-field IMRT. The simultaneous integrated boost (SIB) technique was used to deliver 70 Gy (2.12 Gy per fraction) to the primary tumor and involved nodes; 60 Gy (1.81 Gy per fraction) to the entire nasopharynx and 54 Gy (1.63 Gy per fraction) to elective lymph nodes in 33 fractions. Plans also aimed to keep the mean parotid dose below 26 Gy and limit the maximum doses to the spinal cord and brain stem to 45 and 54 Gy, respectively. Mean parotid gland doses for the two planning techniques were compared using a paired t-test. Target coverage and dose inhomogeneity were evaluated by calculating conformity- (CI) and homogeneity index (HI) values.

Results: Target coverage and dose homogeneity were identical and good for both planning techniques: CI = 1.05 ± 0.08 and 1.05 ± 0.08; HI = 1.08 ± 0.02 and 1.07 ± 0.01 for arc- and static field IMRT, respectively. Mean doses to contralateral parotid glands were 25.73 ± 4.27 and 27.73 ± 3.5 Gy(p = 0.008) for arc- and static field IMRT plans, respectively, whereas mean ipsilateral parotid doses were 30.65 ± 6.25 and 32.55 ± 5.93 Gy (non-significant p-value), respectively. Mean monitor units (MU) per fraction for the 10 patients were considerably lower for arc- than for static field treatments-540.5 ± 130.39 versus 1288.4 ± 197.28 (p < 0.001).

Conclusion: Normal tissues--particularly the parotid glands--are better spared with the arc technique in patients with NPC. MU and treatment times are considerably reduced in arc IMRT plans.

Citing Articles

Quality of life and survival outcome for patients with nasopharyngeal carcinoma treated by volumetric-modulated arc therapy versus intensity-modulated radiotherapy.

Huang T, Tsai M, Chuang H, Chien C, Lin Y, Tsai W Radiat Oncol. 2020; 15(1):84.

PMID: 32307024 PMC: 7168825. DOI: 10.1186/s13014-020-01532-4.

Superiority of intensity-modulated radiation therapy in nasopharyngeal carcinoma with skull-base invasion.

Liao S, Xie Y, Feng Y, Zhou Y, Pan Y, Fan J J Cancer Res Clin Oncol. 2019; 146(2):429-439.

PMID: 31677113 DOI: 10.1007/s00432-019-03067-y.

Slug inhibition increases radiosensitivity of nasopharyngeal carcinoma cell line C666-1.

Yang H, Zhang G, Che X, Yu S Exp Ther Med. 2018; 15(4):3477-3482.

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SmartArc-based volumetric modulated arc therapy can improve the middle ear, vestibule and cochlea sparing for locoregionally advanced nasopharyngeal carcinoma: a dosimetric comparison with step-and-shoot intensity-modulated radiotherapy.

Gao J, Qian T, Tao C, Zhang Y, Zhou Y, Yang J Br J Radiol. 2015; 88(1053):20150052.

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Clinical and dosimetric evaluation of RapidArc versus standard sliding window IMRT in the treatment of head and neck cancer.

Smet S, Lambrecht M, Vanstraelen B, Nuyts S Strahlenther Onkol. 2014; 191(1):43-50.

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