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Strahlentherapie und Onkologie

, Volume 195, Issue 4, pp 327–334 | Cite as

Comparison of treatment plans for a high-field MRI-linac and a conventional linac for esophageal cancer

  • Marcel Nachbar
  • David Mönnich
  • Paul Kalwa
  • Daniel Zips
  • Daniela Thorwarth
  • Cihan GaniEmail author
Original Article

Abstract

Purpose

To compare radiotherapy treatments plans in esophageal cancer calculated for a high-field magnetic resonance imaging (MRI)-linac with plans for a conventional linac.

Materials and methods

Ten patients with esophageal squamous cell carcinomas were re-planned retrospectively using the research version of Monaco (V 5.19.03, Elekta AB, Stockholm, Sweden). Intensity modulated radiotherapy (IMRT) plans with a nine-field step-and-shoot technique and two-arc volumetric modulated arc therapy (VMAT) plans were created for the Elekta MRI-linac and a conventional linac, respectively. The prescribed dose was 60 Gy to the primary tumor (PTV60) and 50 Gy to elective volumes (PTV50). Plans were optimized for optimal coverage of the 60 Gy volume and compared using dose–volume histogram parameters.

Results

All calculated treatment plans met predefined criteria for target volume coverage and organs at risk dose both for MRI-linac and conventional linac. Plans for the MRI-linac had a lower number of segments and monitor units. No significant differences between both plans were seen in terms of V20Gy of the lungs and V40Gy of the heart with slightly higher mean doses to the heart (14.0 Gy vs. 12.5 Gy) and lungs (12.8 Gy vs. 12.2 Gy).

Conclusion

Applying conventional target volume and margin concepts as well as dose-fractionation prescription reveals clinically acceptable dose distributions using hybrid MRI-linac in its current configuration compared to standard IMRT/VMAT. This represents an important prerequisite for future studies to investigate the clinical benefit of MRI-guided radiotherapy exploiting the conceptional advantages such as reduced margins, plan adaptation and biological individualization and hypofractionation.

Keywords

Organs at risk Squamous cell carcinomas  Magnetic resonance imaging Intensity-modulated radiotherapy Volumetric modulated arc therapy  

Vergleich der Behandlungspläne von einem Hochfeld-MRT-Linac und einem konventionellen Linac beim Ösophaguskarzinom

Zusammenfassung

Zielsetzung

Ziel der gegenwärtigen Arbeit ist es, Hochfeld-Magnetresonanztomographie(MRT-)-Linac-Bestrahlungspläne zur Behandlung von Ösophaguskarzinomen mit Plänen, die für einen konventionellen Linearbeschleuniger berechnet wurden, zu vergleichen.

Material und Methoden

Für 10 Patienten mit einem Plattenepithelkarzinom des Ösophagus wurde retrospektiv eine Replanung mit der Forschungsversion von „Monaco“ (V 5.19.03, Elekta AB, Stockholm, Schweden) durchgeführt. Intensitätsmodulierte Bestrahlungs(IMRT)-Pläne in einer Neun-Felder-step-and-shoot-Technik und volumenmodulierte Arc-Therapie(VMAT)-Pläne mit zwei Bögen wurden jeweils für den Elekta-MRT-Linac und für einen konventionellen Linac erstellt. Die verschriebene Dosis betrug 60 Gy für den Primärtumor (PTV60) und 50 Gy für elektiv nodale Areale (PTV50). Die Pläne wurden auf eine optimale Erfassung des 60-Gy-Volumens hin optimiert und über Dosis-Volumen-Histogrammparameter miteinander verglichen.

Ergebnisse

Alle Behandlungspläne erfüllten die vordefinierten Kriterien zur Zielvolumenabdeckung und für die Risikoorgane sowohl für den MRT-Linac als auch für den konventionellen Linac. Die Pläne für den MRT-Linac wiesen eine niedrigere Anzahl von Segmenten und Monitoreinheiten auf. Keine signifikanten Unterschiede zwischen den Plänen wurden in Bezug auf die V20Gy der Lunge und die V40Gy des Herzens gesehen, mit leicht höheren mittleren Herz- (14,0 Gy vs. 12,5 Gy) und Lungendosen (12,8 Gy vs. 12,2 Gy).

Schlussfolgerung

Unter Anwendung konventioneller Zielvolumenkonzepte, Sicherheitssäume und Dosisfraktionierungskonzepte zeigen sich klinisch akzeptable Dosisverteilungen für den MRT-Linac in seiner aktuellen Konfiguration im Vergleich zur Standard-IMRT/VMAT. Dies stellt eine wichtige Voraussetzung für zukünftige Studien dar, die den klinischen Nutzen der MRT-gestützten Strahlentherapie untersuchen und die konzeptionellen Vorteile, wie verminderte Sicherheitssäume, Adaptationen, biologische Individualisierungen sowie Hypofraktionierung, implementieren.

Schlüsselwörter

Risikoorgane Plattenepithelkarzinome Magnetresonanztomographie Intensitätsmodulierte Strahlentherapie Volumenmodulierte Arc-Therapie 

Notes

Funding

We acknowledge technical support from Elekta AB and Philips under a research agreement. However, the sponsors had no part in the design or execution of the study. The MRI-linac installation in Tübingen is funded by the German Research Council (Deutsche Forschungsgemeinschaft, DFG), grant no. ZI 736/2-1. CG is supported by the “Clinician Scientist Program” of the Medical Faculty, Eberhard Karls Universität Tübingen (Funding number: 363-0-0).

Conflict of interest

The Department of Radiation Oncology in Tübingen has a research agreement with Elekta AB (Stockholm, Sweden) giving the authors (Marcel Nachbar, David Mönnich, Paul Kalwa, Daniel Zips, Daniela Thorwarth, Cihan Gani) access to the Monaco research treatment planning system including hardware. There is no further conflict of interest to disclose.

Supplementary material

66_2018_1386_MOESM1_ESM.docx (103 kb)
Figure a: Differences between initial plans generated with individualized beam angles and equidistant beam angles. Positive differences mark an increase in the respective metric for the plans generated with individualized beam angles.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Section for Biomedical Physics, Department of Radiation OncologyUniversity Hospital and Medical Faculty, Eberhard Karls University TübingenTübingenGermany
  2. 2.German Cancer Consortium (DKTK), Partner Site Tübingen; and German Cancer Research Center (DKFZ)HeidelbergGermany
  3. 3.Department of Radiation OncologyUniversity Hospital and Medical Faculty, Eberhard Karls University TübingenTübingenGermany
  4. 4.Gastrointestinal Cancer CenterComprehensive Cancer Center Tübingen-StuttgartTübingenGermany

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