Dosimetric Comparison Between Helical Tomotherapy and Volumetric Modulated Arc Therapy in Patients With Malignant Pleural Mesothelioma

Our plain-English summary of Dosimetric Comparison Between Helical Tomotherapy and Volumetric Modulated Arc Therapy in Patients With Malignant Pleural Mesothelioma, by T. Müdder, G.R. Sarria, C. Henkenberens, et al (Clinical Oncology, 2022).

The study

• Authors: T. Müdder, G.R. Sarria, C. Henkenberens, J. Holz, S. Garbe, F. Röhner, S. Stumpf, T. Buchstab, F.A. Giordano, C. Leitzen
• Journal: Clinical Oncology
• Published: 2022;34(3):164-171
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aims: To carry out a dosimetric comparison and constraints feasibility proof of adjuvant radiotherapy through helical tomotherapy or volumetric modulated arc therapy (VMAT) for malignant pleural mesothelioma patients after pleurectomy/decortication.

Materials And Methods: Retrospective calculations were carried out on previously acquired simulations. A whole-pleura volume with 50.4 Gy in 28 fractions was prescribed, simulating a no residual tumour situation. Calculations were carried out using an anisotropic analytical algorithm with a 2.0 mm grid. Beam-on time, planning target volume (PTV) coverage, homogeneity index and organ at risk exposure were compared.

Results: Sixteen patient plans were calculated per device. Constraints were met overall by both modalities. For helical tomotherapy and VMAT plans, median beam-on times were 13.8 (11.6-16.1) min and 6.4 (6.1-7.0) min; P = 0.006. The median left-sided radiotherapy PTV D98 were 48.1 (48.0-48.8) Gy and 47.6 (46.5-48.3) Gy; P = 0.023. No significant difference for right-sided radiotherapy was found. PTV D2 for left-sided radiotherapy was higher with VMAT (P = 0.014). For right-sided radiotherapy, helical tomotherapy showed higher doses (P = 0.039). No homogeneity index differences for left-sided radiotherapy (P = 1.00) and right-sided radiotherapy (P = 0.598) were seen. Significant organ at risk exposure differences were found on left-sided radiotherapy whole-lung V20, as well as D50 (both P = 0.008). Higher contralateral lung and ipsilateral kidney exposures were found with VMAT plans for both treatment sides.

Conclusion: Adjuvant radiotherapy after pleurectomy/decortication in malignant pleural mesothelioma patients, with a VMAT- or helical tomotherapy-based platform, is dosimetrically feasible. Lung sparing was mostly improved with helical tomotherapy. Technique selection must be carried out according to availability and clinical criteria.

Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.

In plain English

This was a radiotherapy planning study from University Hospital Bonn, Germany. It did not study asbestos exposure. The authors used earlier planning scans of 16 patients with malignant pleural mesothelioma who had had pleurectomy/decortication with no residual tumour (8 right-sided, 8 left-sided). For each patient they calculated plans on two machines, helical tomotherapy and volumetric modulated arc therapy (VMAT), aiming 50.4 Gy at the whole pleura in 1.8 Gy doses. The comparison used calculated plans only. Median beam-on time was 13.8 minutes with tomotherapy and 6.4 minutes with VMAT. With machine-movement time added, VMAT took 11 minutes, which was not significantly different. For left-sided plans, the target-coverage goal was met in 8 of 8 tomotherapy plans and 4 of 8 VMAT plans, and tomotherapy gave lower doses to the lungs. On both sides the opposite lung received less with tomotherapy. Dose uniformity did not differ. The authors concluded that the techniques were comparable for target coverage and that lung sparing was mostly better with tomotherapy. They cautioned that no clear clinical benefit could be inferred from the mostly small differences.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective radiotherapy planning (dosimetric) comparison study; plans for both techniques were calculated on previously acquired planning scans
• Who was studied: 16 patients with malignant pleural mesothelioma treated at the authors' centre (Department of Radiation Oncology, University Hospital Bonn, Germany) after pleurectomy/decortication with no residual tumour; 13 had been evaluated in the group's prior publication; median age 66 (range 47 to 78); 4 female, 12 male; 8 right-sided, 8 left-sided. Dates not given.
• Exposure: No asbestos exposure was studied. The comparison was between two radiotherapy techniques, helical tomotherapy and VMAT, planned to deliver 50.4 Gy to the whole pleura in single doses of 1.8 Gy after pleurectomy/decortication.
• Main results:
  • All 16 patients: median beam-on time was 13.8 (11.6 to 16.1) min for helical tomotherapy and 6.4 (6.1 to 7.0) min for VMAT, P = 0.006.
  • When gantry-releasing time was added, the median VMAT procedure time was 11 (10.6 to 12.3) min, and the difference from helical tomotherapy was not statistically significant (P = 0.084).
  • Left-sided plans: median target D98 was 48.1 (48.0 to 48.8) Gy for helical tomotherapy and 47.6 (46.5 to 48.3) Gy for VMAT (P = 0.023). The coverage constraint was met in 8/8 helical tomotherapy plans and 4/8 VMAT plans.
  • Left-sided plans, combined lungs: median V20 was 26.7% (15.4 to 33.2) for helical tomotherapy and 31.1% (23.6 to 37.1) for VMAT (P = 0.008). Median D50 was 5.2 (3.9 to 5.8) Gy and 5.8 (4.8 to 6.9) Gy (P = 0.008).
  • Left-sided plans, contralateral (right) lung: median D50 was 3.6 (3.2 to 3.8) Gy for helical tomotherapy and 4.6 (4.0 to 5.4) Gy for VMAT (P = 0.014). Median V5 was 21.2% (19.9 to 29.2) and 37.2% (20.1 to 59.7) (P = 0.008).
  • Right-sided plans: median target D98 was 48.4 (47.9 to 48.8) Gy for helical tomotherapy and 48.9 (47.7 to 49.5) Gy for VMAT (P = 0.05).
  • Right-sided plans, combined lungs: median V20 was 34.8% (19.8 to 41.4) for helical tomotherapy and 35.6% (21.6 to 44.5) for VMAT (P = 0.844).
  • Right-sided plans, contralateral (left) lung: median D50 was 3.6 (3.18 to 3.80) Gy for helical tomotherapy and 4.6 (3.98 to 5.39) Gy for VMAT (P = 0.008). Median V5 was 27.0% (12.7 to 34.0) and 36.0% (25.1 to 72.1) (P = 0.008).
  • Right-sided plans, ipsilateral kidney: median V18 was 15.4% (11.7 to 41.5) for helical tomotherapy and 24.1% (16.5 to 39.0) for VMAT (P = 0.023).
  • Left-sided plans: the homogeneity index did not differ between helical tomotherapy and VMAT (P = 1.00). For right-sided plans the P value was 0.598.
• The authors' conclusion: The authors concluded that adjuvant radiotherapy after pleurectomy/decortication in malignant pleural mesothelioma, delivered with either VMAT or helical tomotherapy, is dosimetrically comparable for target volume coverage. They found lung sparing mostly improved with helical tomotherapy, and said technique choice should follow availability and clinical criteria. They also cautioned that no clear clinical benefit could be inferred from the mostly small dose differences.
• Limitations the authors state:
  • The study was retrospective, and its set-up configurations were specific to the systems available at the authors' department, so they might not be reproducible everywhere.
  • No boost planning was performed, which might lead to different dosimetric and clinical outcomes.
  • The authors said the statistically significant advantages of helical tomotherapy should be interpreted carefully, because the dose differences were mostly small and no clear clinical benefit could be inferred.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Pleurectomy/Decortication (P/D), Pleura.

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