• Tim Dijkema, Cornelis P J Raaijmakers, Randall K Ten Haken, Judith M Roesink, Pètra M Braam, Anette C Houweling, Marinus A Moerland, Avraham Eisbruch, and Chris H J Terhaard.
• Department of Radiotherapy, University Medical Center Utrecht, The Netherlands. T.Dijkema@umcutrecht.nl
• Int. J. Radiat. Oncol. Biol. Phys. 2010 Oct 1; 78 (2): 449-53.

PurposeTo analyze the combined and updated results from the University of Michigan and University Medical Center Utrecht on normal tissue complication probability (NTCP) of the parotid gland 1 year after radiotherapy (RT) for head-and-neck (HN) cancer.Patients And MethodsA total of 222 prospectively analyzed patients with various HN malignancies were treated with conventional and intensity-modulated RT. Stimulated individual parotid gland flow rates were measured before RT and 1 year after RT using Lashley cups at both centers. A flow ratio <25% of pretreatment was defined as a complication. The data were fitted to the Lyman-Kutcher-Burman model.ResultsA total of 384 parotid glands (Michigan: 157; Utrecht: 227 glands) was available for analysis 1 year after RT. Combined NTCP analysis based on mean dose resulted in a TD(50) (uniform dose leading to 50% complication probability) of 39.9 Gy and m (steepness of the curve) of 0.40. The resulting NTCP curve had good qualitative agreement with the combined clinical data. Mean doses of 25-30 Gy were associated with 17-26% NTCP.ConclusionsA definite NTCP curve for parotid gland function 1 year after RT is presented, based on mean dose. No threshold dose was observed, and TD(50) was equal to 40 Gy.2010 Elsevier Inc. All rights reserved.

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