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VMAT and Step-and-Shoot IMRT in Head and Neck Cancer

A Comparative Plan Analysis

VMAT und Step&Shoot-IMRT bei Kopf-Hals-Tumor-Patienten: Eine vergleichende Analyse

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Purpose:

Rotational IMRT is a new technique, whose value still has to be assessed. We evaluated its adequacy for the treatment of head and neck (H&N) cancer compared to the well-established step-and-shoot IMRT.

Materials and Methods:

A total of 15 patients, who were treated with either IMRT (13 patients) or VMAT (2 patients) in the H&N region, were chosen. For each patient, a treatment plan with the respective other technique was calculated. To compare the resulting dose distributions, the dose–volume histograms (DVHs) were evaluated. To quantify the differences, a new quality index (QI) was introduced, as a measure of the planning target volume (PTV) coverage and homogeneity. A conformity function (CF) was defined to estimate normal tissue sparing.

Results:

The QI for VMAT amounts to 36.3, whereas for IMRT the mean value is 66.5, indicating better PTV coverage as well as less overdosage for the rotational technique. While the sparing of organs at risk (OAR) was similar for both techniques, the CF shows a significantly better sparing of healthy tissue for all doses with VMAT treatment.

Conclusions:

VMAT results in dose distributions for H&N patients that are at least comparable with treatments performed with step-and-shoot IMRT. Two new tools to quantify the quality of dose distributions are presented and have proven to be useful.

Zielsetzung:

Rotationsbestrahlung mit Intensitätsmodulierung ist eine neue Technik, deren Wert erst noch beurteilt werden muss. Wir untersuchten deren Eignung für die Behandlung von Kopf-Hals-(H&N-)Tumoren im Vergleich zu etablierter Step&Shoot-IMRT.

Material und Methoden:

Es wurden 15 Patienten ausgewählt, die mit IMRT (13 Patienten) oder VMAT (2 Patienten) in der H&N-Region behandelt wurden. Für jeden wurde ein Bestrahlungsplan mit der jeweils anderen Technik berechnet. Um die resultierenden Dosisverteilungen zu vergleichen, wurden Dosis-Volumen Histogramme (DVHs) ausgewertet. Zur Quantifizierung der Unterschiede wurde ein neuer Qualitätsindex (QI) eingeführt, der ein Maß für die Dosisabdeckung und -homogenität innerhalb des PTV ist. Eine Konformitätsfunktion (CF) wurde definiert, um die Nomalgewebeschonung abzuschätzen.

Ergebnisse:

Der QI für VMAT beträgt 36,3, während sich der Mittelwert für IMRT auf 66,5 beläuft, was eine bessere Dosisabdeckung und -homogenität bei der Rotationsbestrahlung anzeigt. Die Schonung der Risikoorgane war für beide Techniken ähnlich; der CF zeigte eine deutlich bessere Normalgewebeschonung für VMAT bei allen Dosiswerten.

Schlussfolgerung:

VMAT erlaubt für die Behandlung von H&N-Patienten Dosisverteilungen zu erzeugen, die mindestens vergleichbar sind mit denen, die mit Step&Shoot-IMRT machbar sind. Zwei neue Größen zur Quantifizierung der Qualität von Dosisverteilungen wurden präsentiert und deren Nutzen gezeigt.

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Authors and Affiliations

  1. Klinik für Strahlenheilkunde, Uniklinik Freiburg, Freiburg, Germany

    Rolf Wiehle, Stefan Knippen, Anca-Ligia Grosu, Gregor Bruggmoser & Norbert Hodapp

  2. Klinik für Strahlenheilkunde, Uniklinik Freiburg, Robert-Koch-Str. 3, 79106, Freiburg, Germany

    Rolf Wiehle

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  1. Rolf Wiehle
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  2. Stefan Knippen
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  3. Anca-Ligia Grosu
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  4. Gregor Bruggmoser
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  5. Norbert Hodapp
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Correspondence to Rolf Wiehle.

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Wiehle, R., Knippen, S., Grosu, AL. et al. VMAT and Step-and-Shoot IMRT in Head and Neck Cancer. Strahlenther Onkol 187, 820–825 (2011). https://doi.org/10.1007/s00066-011-2267-x

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  • DOI: https://doi.org/10.1007/s00066-011-2267-x

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