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CT-based dose recalculations in head and neck cancer radiotherapy: comparison of daily dose recalculations to less time-consuming approaches

  • Simon Wagenblast
  • Severin Kampfer
  • Kai J. Borm
  • Stephanie E. Combs
  • Steffi U. Pigorsch
  • Marciana-Nona Duma
Original Article
  • 19 Downloads

Abstract

Background

The goal of this study was to investigate if daily dose recalculations are necessary or if less time-consuming approaches can be used to identify dose differences to the planned dose in patients with head and neck cancers (H&N).

Methods

For 12 H&N patients treated with helical tomotherapy, daily dose calculations were performed retrospectively. Four different summation doses (SuDo) were calculated: DayDo (daily dose calculation), MVCTx2, MVCTx5, and MVCTx10 (dose calculations every second, fifth, and tenth fraction). Dose recalculations were depicted on the last contoured mega voltage CT (MVCT). The DayDo was compared to the planned dose and to the less time-consuming SuDo scenarios. The doses were assessed for the planning target volume (PTV) and the organs at risk (OARs): mandible (mand), spinal cord (SC), spinal cord +5 mm (SC+5 mm), parotid glands (PG).

Results

The ipsilateral PG, contralateral PG, and PTV volume decreased by −22.5% (range: −34.8 to 5.2%), −19.5% (−31.5 to 15.8%), and −2.6% (−16.7 to 0.2%), respectively. There was a significant median mean dose (Dmean) dose difference for DayDo compared to the planned dose for PG total of 1.9 Gy (−3.3 to 7.3 Gy). But less time-consuming SuDo compared to DayDo showed statistically significant but not clinically relevant (<2%) dose differences for several organs. Hence the small dose difference to the gold standard (DayDo), we recommend dose recalculations every fifth MVCT in order to identify the occurrence of dose differences compared to the planned dose.

Conclusion

Daily dose calculations are the most precise to assess dose differences between actual and planned dose. Dose recalculations on every fifth MVCT (i. e., weekly control CTs) are an applicable and time-saving way of identifying patients with significant dose differences compared to the planned dose.

Keywords

MVCT cancers Adaptive radiotherapy Helical tomotherapy IGRT IMRT 

CT-basierte Dosisneuberechnung bei der Strahlentherapie von Kopf-Hals-Tumoren: Vergleich der täglichen Dosisneuberechnung mit weniger zeitaufwändigen Ansätzen

Zusammenfassung

Hintergrund

Ziel dieser Studie war es, zu untersuchen, ob die tägliche Dosisneuberechnung (DayDo) nötig ist und ob weniger zeitaufwendige Dosisberechnungen geeignet sind, um Dosisunterschiede bei der Planungsdosis von Patienten mit Kopf-Hals-Tumoren (H&N) zu identifizieren.

Methoden

Insgesamt 12 H&N-Patienten wurden mittels Tomotherapie bestrahlt und tägliche Dosisberechnungen wurden retrospektiv durchgeführt. Es wurden 4 verschiedene Szenarien (SuDo) berechnet: DayDo (tägliche Dosisberechnung), MVCTx2, MVCTx5 und MVCTx10 (Dosisberechnungen jede zweite, fünfte und zehnte Fraktion). Die Dosis-Neuberechnungen wurden auf dem letzten MVCT dargestellt. Die tägliche Dosisberechnung wurde mit der Planungsdosis und den weniger zeitaufwendigen Szenarien verglichen. Des Weiteren wurden die Volumenveränderungen im Verlauf der Strahlentherapie erfasst. Bestimmt wurden die Dosen für das Zielvolumen (PTV) und für die Risikoorgane (OARs): Unterkiefer (mand), Rückenmark (SC), Rückenmark +5 mm (SC+5 mm) und Ohrspeicheldrüsen (PG).

Ergebnisse

Das Volumen der ipsi- und kontralateralen PG sowie das PTV sanken um −22,5 % (Spanne −34,8–5,2 %), −19,5 % (Spanne −31,5–15,8 %) bzw. −2,6 % (Spanne −16,7–0,2 %). Es gab eine statistisch signifikante Dosisdifferenz der medianen Dmean beider PG zusammen um 1,9 Gy (Spanne −3,3–7,3 Gy). Für verschiedene OARs existierten für die weniger zeitaufwändigen Szenarien im Vergleich zur DayDo zwar statistisch signifikante, aber klinisch nicht relevante Dosisunterschiede (<2 %). Aufgrund der klinisch irrelevanten Unterschiede sind Dosisberechnungen jedes fünften MVCT ein einfaches und zeitsparendes Verfahren, um Dosisunterschiede zwischen Planungsdosis und wirklicher Dosis festzustellen.

Schlussfolgerung

Tägliche Dosisneuberechnung ist die genaueste Methode, um Dosisunterschiede zwischen Planung und tatsächlicher Dosis zu ermitteln. Aber Dosisberechnung jedes fünften MVCT ist ein zeitsparendes und einfaches Verfahren, um Dosisunterschiede zwischen Planungsdosis und wirklicher Dosis festzustellen.

Schlüsselwörter

Kopf- und Halstumore Adaptive Strahlentherapie Helikale Tomotherapie IGRT IMRT 

Notes

Conflict of interest

S. Kampfer received 2015 a professional fee from Accuray. S. Wagenblast, K.J. Borm, S.E. Combs, S.U. Pigorsch, and M.-N. Duma declare that they have no competing interests.

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Copyright information

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

Authors and Affiliations

  1. 1.Department of Radiation Oncology, Klinikum rechts der IsarTechnical University MunichMunichGermany
  2. 2.Faculty of MedicineTechnical UniversityMunichGermany
  3. 3.Deutsches Konsortium für Translationale Krebsforschung (DKTK)-Partner Site MunichMunichGermany
  4. 4.Institute of Innovative RadiotherapyHelmholtzzentrum MünchenMunichGermany

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