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Evaluation of radiotherapy techniques for radical treatment of lateralised oropharyngeal cancers

Dosimetry and NTCP

Untersuchung von Strahlentherapieverfahren zur radikalen Bestrahlung von unilateralen Oropharynxtumoren

Dosimetrie und Komplikationswahrscheinlichkeit in Normalgeweben

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The aim of this study was to investigate potential advantages and disadvantages of three-dimensional conformal radiotherapy (3DCRT), multiple fixed-field intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) in terms of dose to the planning target volume (PTV), organs at risk (OARs) and normal tissue complication probability (NTCP) for delivering ipsilateral radiotherapy.

Materials and methods

3DCRT, IMRT and VMAT were compared in patients with well-lateralised primary tonsillar cancers who underwent primary radical ipsilateral radiotherapy. The following parameters were compared: conformity index (CI); homogeneity index (HI); dose–volume histograms (DVHs) of PTVs and OARs; NTCP, risk of radiation-induced cancer and dose accumulation during treatment.


IMRT and VMAT were superior to 3DCRT in terms of CI, HI and dose to the target volumes, as well as mandible and dose accumulation robustness. The techniques were equivalent in terms of dose and NTCP for the contralateral oral cavity, contralateral submandibular gland and mandible, when specific dose constraint objectives were used on the oral cavity volume. Although the volume of normal tissue exposed to low-dose radiation was significantly higher with IMRT and VMAT, the risk of radiation-induced secondary malignancy was dependant on the mathematical model used.


This study demonstrates the superiority of IMRT/VMAT techniques over 3DCRT in terms of dose homogeneity, conformity and consistent dose delivery to the PTV throughout the course of treatment in patients with lateralised oropharyngeal cancers. Dosimetry and NTCP calculations show that these techniques are equivalent to 3DCRT with regard to the risk of acute mucositis when specific dose constraint objectives were used on the contralateral oral cavity OAR.



Das Ziel dieser Studie war die Untersuchung potenzieller Vor- und Nachteile der dreidimensionalen, konformalen Strahlentherapie (3DCRT), der intensitätsmodulierten Strahlentherapie (IMRT) in Step-and-Shoot-Technik und der intensitätsmodulierten Rotationstherapie (“volumetric-modulated arc therapy”, VMAT) für die ipsilaterale Bestrahlung von Oropharynxtumoren hinsichtlich der Dosisverteilung im Planungszielvolumen (PTV), den Risikoorganen (OAR) und der Komplikationswahrscheinlichkeit in Normalgeweben (NTCP).

Materialien und Methoden

Für die radikale Primärtherapie unterschiedlicher Fälle von streng unilateralen primären Tonsillenkarzinomen wurden Dosisverteilungen von 3DCRT, IMRT und VMAT verglichen. Hierfür wurden Konformitätsindex (CI), Homogenitätsindex (HI), Dosis-Volumen-Histogramme (DVH) des PTV und der OAR, NTCP, Risiko von strahleninduzierten Zweittumoren und die aufsummierte applizierte Gesamtdosis untersucht.


Die Bestrahlungspläne von IMRT und VMAT waren in Bezug auf CI, HI, Dosisverteilung im Zielvolumen und im Unterkiefer sowie der tatsächlich applizierten Dosis der 3DCRT überlegen. Bezüglich der Dosisverteilung, der NTCP der kontralateralen Mundhöhle, Gl. submandibularis und des Unterkiefers bei Anwendung einer dedizierten Dosisvolumenbeschränkung der Mundhöhle waren die Techniken äquivalent. Obwohl das Niedrigdosisvolumen bei IMRT und VMAT signifikant höher war als bei 3DCRT, war das erwartete Risiko strahleninduzierter Zweittumoren abhängig vom verwendeten mathematischen Modell.


Die untersuchten IMRT-/VMAT-Techniken sind der 3DCRT bei der Bestrahlung streng unilateraler oropharyngealer Tumoren in Bezug auf die Dosishomogenität, Konformität und konsistente Bestrahlung des PTV während der gesamten Behandlungsdauer überlegen. Dosimetrie und NTCP-Berechnungen zeigen, dass diese Techniken in Bezug auf das Risiko einer akuten Mukositis bei Anwendung einer spezifischen Dosisbeschränkung auf die kontralaterale Mundhöhle äquivalent zu 3DCRT sind.

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This work was undertaken in The Royal Marsden NHS Foundation Trust which received a proportion of its funding from the NHS Executive; the views expressed in this publication are those of the authors and not necessarily those of the NHS Executive.  This work was supported by Cancer Research UK Programme Grants C46/A10588 and C7224/A13407.  The authors also acknowledge the support of the National Institute for Health Research Royal Marsden and Institute of Cancer Research Biomedical Research Centre.

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Correspondence to S. A. Bhide.

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D. McQuaid, A. Dunlop, S. Nill, C. Franzese, C. M. Nutting, K. J. Harrington, K. L. Newbold and S.A. Bhide state that there are no conflicts of interest.

The accompanying manuscript does not include studies on humans or animals.

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McQuaid, D., Dunlop, A., Nill, S. et al. Evaluation of radiotherapy techniques for radical treatment of lateralised oropharyngeal cancers. Strahlenther Onkol 192, 516–525 (2016).

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