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Target coverage and dose criteria based evaluation of the first clinical 1.5T MR-linac SBRT treatments of lymph node oligometastases compared with conventional CBCT-linac treatment.

Authors
  • Winkel, Dennis1
  • Bol, Gijsbert H2
  • Werensteijn-Honingh, Anita M2
  • Intven, Martijn P W2
  • Eppinga, Wietse S C2
  • Hes, Jochem2
  • Snoeren, Louk M W2
  • Sikkes, Gonda G2
  • Gadellaa-van Hooijdonk, Christa G M2
  • Raaymakers, Bas W2
  • Jürgenliemk-Schulz, Ina M2
  • Kroon, Petra S2
  • 1 Department of Radiotherapy, University Medical Center, Utrecht, The Netherlands. Electronic address: [email protected] , (Netherlands)
  • 2 Department of Radiotherapy, University Medical Center, Utrecht, The Netherlands. , (Netherlands)
Type
Published Article
Journal
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
Publication Date
Mar 05, 2020
Volume
146
Pages
118–125
Identifiers
DOI: 10.1016/j.radonc.2020.02.011
PMID: 32146257
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Patients were treated at our institute for single and multiple lymph node oligometastases on the 1.5T MR-linac since August 2018. The superior soft-tissue contrast and additional software features of the MR-linac compared to CBCT-linacs allow for online adaptive treatment planning. The purpose of this study was to perform a target coverage and dose criteria based evaluation of the clinically delivered online adaptive radiotherapy treatment compared with conventional CBCT-linac treatment. Patient data was used from 14 patients with single lymph node oligometastases and 6 patients with multiple (2-3) metastases. All patients were treated on the 1.5T MR-linac with a prescribed dose of 5 × 7 Gy to 95% of the PTV and a CBCT-linac plan was created for each patient. The difference in target coverage between these plans was compared and plans were evaluated based on dose criteria for each fraction after calculating the CBCT-plan on the daily anatomy. The GTV coverage was evaluated based on the online planning and the post-delivery MRI. For both single and multiple lymph node oligometastases the GTV V35Gy had a median value of 100% for both the MR-linac plans and CBCT-plans pre- and post-delivery and did not significantly differ. The percentage of plans that met all dose constraints was improved from 19% to 84% and 20% to 67% for single and multiple lymph node cases, respectively. Target coverage and dose criteria based evaluation of the first clinical 1.5T MR-linac SBRT treatments of lymph node oligometastases compared with conventional CBCT-linac treatment shows a smaller amount of unplanned violations of high dose criteria. The GTV coverage was comparable. Benefit is primarily gained in patients treated for multiple lymph node oligometastases: geometrical deformations are accounted for, dose can be delivered in one plan and margins can be reduced. Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.

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