Early experience with intensity modulated proton therapy for lung-intact mesothelioma: A case series

Our plain-English summary of Early experience with intensity modulated proton therapy for lung-intact mesothelioma: A case series, by H.Y. Pan, S. Jiang, J. Sutton, et al (Practical Radiation Oncology, 2015).

The study

• Authors: H.Y. Pan, S. Jiang, J. Sutton, Z. Liao, W.W. Chance, S.J. Frank, X.R. Zhu, H. Li, H.P. Fontanilla, X. Zhang, D.R. Gomez
• Journal: Practical Radiation Oncology
• Published: 2015;5(4):e345-53
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: The purpose of this study was to describe our experience implementing intensity modulated proton therapy (IMPT) for lung-intact malignant pleural mesothelioma (MPM), including patient selection, treatment planning, dose verification, and process optimization.

Methods And Materials: Seven patients with epithelioid MPM were reviewed; 6 underwent pleurectomy, whereas 1 had biopsy alone. Four patients received IMPT and 3 received intensity modulated radiation therapy. Treatment plans for the other modality were created for dosimetric comparisons. Quality assurance processes included dose verification and robustness analysis. Image-guided setup was performed with the first isocenter, and couch shifts were applied to reposition to the second isocenter.

Results: Treatment with IMPT was well tolerated and completed without breaks. IMPT plans were designed with 2 isocenters, 4 beams, and ≤64 energy layers per beam. Dose verification processes were completed in 3 hours. Total daily treatment time was approximately 45 minutes (20 minutes for setup and 25 minutes for delivery). IMPT produced lower mean doses to the contralateral lung, heart, esophagus, liver, and ipsilateral kidney, with increased contralateral lung sparing when mediastinal boost was required for nodal disease.

Conclusions: Our initial experience showed that IMPT was feasible for routine care of patients with lung-intact MPM.

Copyright © 2015 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

In plain English

This case series from The University of Texas MD Anderson Cancer Center in Houston looked back at 7 patients with epithelioid malignant pleural mesothelioma who received radiation to one side of the chest between 2010 and 2014, with the lung left in place. Six had pleurectomy/decortication surgery and one had biopsy only. Four received intensity modulated proton therapy (IMPT) and three received intensity modulated radiation therapy (IMRT). Each patient's plan was also redrawn with the other method so the two could be compared. The article does not discuss asbestos exposure. The authors reported that IMPT was well tolerated and completed without breaks. In the plan comparison, IMPT gave lower mean doses to the opposite lung (1.7 versus 5.0 Gy), heart, esophagus, liver and same-side kidney. Doses to the treated lung were similar. Daily treatment took about 45 minutes. Dose checks were shortened from more than 8 hours to about 3. The authors concluded that IMPT was feasible for clinical use. They noted that the study was small and retrospective, and that longer follow-up is needed.

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 case series with a treatment-plan (dosimetric) comparison of IMPT versus IMRT
• Who was studied: 7 patients (6 male, 1 female, aged 51 to 77) with biopsy-proven epithelioid malignant pleural mesothelioma treated at MD Anderson Cancer Center, Houston, 2010 to 2014. Four received IMPT and three received IMRT. Six had pleurectomy/decortication and one had biopsy alone. All received cisplatin and pemetrexed.
• Exposure: No asbestos exposure is described. The study concerns radiation treatment to one side of the chest: 45 Gy in 25 fractions to the planning target volume, with a boost of 60 Gy in 25 fractions to gross disease, delivered by IMPT or IMRT.
• Main results:
  • The authors reported that IMPT was well tolerated and completed without breaks (the 4 IMPT patients).
  • In the plan comparison for the 7 patients, IMPT produced lower mean doses than IMRT to the contralateral lung, heart, esophagus, liver, and ipsilateral kidney.
  • Mean dose to the contralateral lung was 1.7 Gy with IMPT versus 5.0 Gy with IMRT (P = .01). Doses to the treated lung were similar with both techniques.
  • The proportion of the contralateral lung receiving 5 Gy was 32.7% with IMRT versus 5.3% with IMPT (P = .02).
  • Mean heart dose was lower with IMPT in all patients (median reduction 10.8 Gy; range 7.1 to 12.6 Gy).
  • Daily IMPT treatment took about 45 minutes: 20 minutes for setup and 25 minutes for delivery.
  • Dose-verification quality checks took more than 8 hours for the initial patients. After streamlining to 12 measurements, they took about 3 hours.
  • In one case, changes in the treated lung's volume during treatment compromised target coverage and required replanning.
• The authors' conclusion: The authors concluded that IMPT was feasible for clinical use in lung-intact malignant pleural mesothelioma. They stated that further study with more patients and longer follow-up is needed to determine whether the dose differences translate into meaningful improvements in clinical outcomes.
• Limitations the authors state:
  • The study was retrospective and had a small sample size.
  • Specialized, partly in-house planning tools were required, which may reduce how well the findings apply elsewhere.
  • Larger numbers of patients and longer follow-up are needed to compare clinical outcomes after IMPT with those after IMRT.

Topics

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

Medical terms in this study, explained in our Lexicon: Proton Therapy, Mesothelioma, Pleural Mesothelioma, Epithelioid, Biopsy.

Related studies

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• Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs — L. Kuo, E.D. Yorke, et al. (2016)
• Is there a single spot size and grid for intensity modulated proton therapy? Simulation of head and neck, prostate and mesothelioma cases — L. Widesott, A.J. Lomax, et al. (2012)
• Adjuvant intensity-modulated proton therapy in malignant pleural mesothelioma. A comparison with intensity-modulated radiotherapy and a spot size variation assessment — S. Lorentini, M. Amichetti, et al. (2012)
• Patterns of failure, toxicity, and survival after extrapleural pneumonectomy and hemithoracic intensity-modulated radiation therapy for malignant pleural mesothelioma — D.R. Gomez, D.S. Hong, et al. (2013)
• Single-institution experience of intensity-modulated radiotherapy for malignant pleural mesothelioma at University of Catania — C. Spatola, C. Militello, et al. (2018)

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