NTCP Modeling of Subacute/Late Laryngeal Edema Scored by Fiberoptic Examination
- Prostate Program, Istituto Nazionale dei Tumori, Milano (Italy)
- Medical Physics, San Raffaele Scientific Institute, Milano (Italy)
- Radiation Oncology, University of Texas Medical Branch, Galveston, TX (United States)
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 alpha/beta = 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 <30-35 Gy should drastically reduce the risk of G2-G3 edema.
- OSTI ID:
- 21367482
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 75, Issue 3; Other Information: DOI: 10.1016/j.ijrobp.2009.04.087; PII: S0360-3016(09)00719-6; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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