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Author Spotlight: Optimizing EAS with Long Electrodes for Enhanced Cochlear Coverage and Hearing Preservation
Published on: October 11, 2024
Normal tissue complication probability modeling for cochlea constraints to avoid causing tinnitus after head-and-neck
Tsair-Fwu Lee1,2, Shyh-An Yeh3,4,5, Pei-Ju Chao6,7
1Medical Physics and Informatics Laboratory of Electronics Engineering, National Kaohsiung University of Applied Sciences, 415, Chien Kung Road, San-Min District, Kaohsiung, 80778, Taiwan, ROC. tflee@kuas.edu.tw.
Background:
Radiation-induced tinnitus is a side effect of radiotherapy in the inner ear for cancers of the head and neck. Effective dose constraints for protecting the cochlea are under-reported. The aim of this study is to determine the cochlea dose limitation to avoid causing tinnitus after head-and-neck cancer (HNC) intensity-modulated radiation therapy (IMRT).
Methods:
In total 211 patients with HNC were included; the side effects of radiotherapy were investigated for 422 inner ears in the cohort. Forty-nine of the four hundred and twenty-two samples (11.6%) developed grade 2+ tinnitus symptoms after IMRT, as diagnosed by a clinician. The Late Effects of Normal Tissues-Subjective, Objective, Management, Analytic (LENT-SOMA) criteria were used for tinnitus evaluation. The logistic and Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) models were used for the analyses.
Results:
The NTCP-fitted parameters were TD 50 = 46.31 Gy (95% CI, 41.46-52.50), γ 50 = 1.27 (95% CI, 1.02-1.55), and TD 50 = 46.52 Gy (95% CI, 41.91-53.43), m = 0.35 (95% CI, 0.30-0.42) for the logistic and LKB models, respectively. The suggested guideline TD 20 for the tolerance dose to produce a 20% complication rate within a specific period of time was TD 20 = 33.62 Gy (95% CI, 30.15-38.27) (logistic) and TD 20 = 32.82 Gy (95% CI, 29.58-37.69) (LKB).
Conclusions:
To maintain the incidence of grade 2+ tinnitus toxicity <20% in IMRT, we suggest that the mean dose to the cochlea should be <32 Gy. However, models should not be extrapolated to other patient populations without further verification and should first be confirmed before clinical implementation.
