NTCP Modeling of Subacute/Late Laryngeal Edema Scored by Fiberoptic Examination

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Abstract

Purpose: Finding best-fit parameters of normal tissue complication probability (NTCP) models for laryngeal edema after radiotherapy for head and neck cancer. Methods and Materials: Forty-eight patients were considered for this study who met the following criteria: (1) grossly uninvolved larynx, (2) no prior major surgery except for neck dissection and tonsillectomy, (3) at least one fiberoptic examination of the larynx within 2 years from radiotherapy, (4) minimum follow-up of 15 months. Larynx dose-volume histograms (DVHs) were corrected into a linear quadratic equivalent one at 2 Gy/fr with α/β = 3 Gy. Subacute/late edema was prospectively scored at each follow-up examination according to the Radiation Therapy Oncology Group scale. G2-G3 edema within 15 months from RT was considered as our endpoint. Two NTCP models were considered: (1) the Lyman model with DVH reduced to the equivalent uniform dose (EUD; LEUD) and (2) the Logit model with DVH reduced to the EUD (LOGEUD). The parameters for the models were fit to patient data using a maximum likelihood analysis. Results: All patients had a minimum of 15 months follow-up (only 8/48 received concurrent chemotherapy): 25/48 (52.1%) experienced G2-G3 edema. Both NTCP models fit well the clinical data: with LOGEUD the relationship between EUD and NTCP can be described with TD50 = 46.7 ± 2.1 Gy, n = 1.41 ± 0.8 and a steepness parameter k = 7.2 ± 2.5 Gy. Best fit parameters for LEUD are n = 1.17 ± 0.6, m = 0.23 ± 0.07 and TD50 = 47.3 ± 2.1 Gy. Conclusions: A clear volume effect was found for edema, consistent with a parallel architecture of the larynx for this endpoint. On the basis of our findings, an EUD

Original languageEnglish
Pages (from-to)915-923
Number of pages9
JournalInternational Journal of Radiation Oncology Biology Physics
Volume75
Issue number3
DOIs
Publication statusPublished - Nov 1 2009

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Keywords

  • Head and neck radiotherapy
  • IMRT
  • Laryngeal edema
  • NTCP

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Cancer Research

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