Dosimetric Correlates of Pulmonary Toxicity in Patients with Malignant Pleural Mesothelioma Receiving Radiation Therapy to the Intact Lungs

Our plain-English summary of Dosimetric Correlates of Pulmonary Toxicity in Patients with Malignant Pleural Mesothelioma Receiving Radiation Therapy to the Intact Lungs, by M.R. Thompson, V.A. Dumane, S.A. Lazarev, et al (Practical Radiation Oncology, 2019).

The study

• Authors: M.R. Thompson, V.A. Dumane, S.A. Lazarev, Y. Zia, K.E. Rosenzweig
• Journal: Practical Radiation Oncology
• Published: 2019;9(3):e331-e337
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: We aimed to determine dose-volume constraints that correlate with severe (grade ≥3) radiation pneumonitis (RP) in patients diagnosed with malignant pleural mesothelioma, treated using volumetric modulated arc therapy.

Methods And Materials: Data from 40 patients with malignant pleural mesothelioma who underwent pleurectomy decortication and adjuvant radiation therapy at our institution between December 2010 and October 2016 were retrospectively analyzed. Dosimetric variables for the absolute volume and percentage volume of the ipsilateral lung, contralateral lung, and heart were recorded. Events of RP were assessed using the Common Terminology Criteria for Toxicity and Adverse Events, version 4.0. The statistical analysis with Wilcoxon rank-sum, Spearman rank correlation, and receiver operating characteristic curves was computed using MATLAB V9.1, RV3.4, and SAS V9.4.

Results: Of the 40 patients, 26 patients (65%) were male. The median age at the time of diagnosis was 66.5 years (range, 44-84 years). The median prescription dose was 45 Gy (range, 30-54 Gy). Five patients (12.5%) had grade ≥3 RP. The incidence of grade≥ 3 RP showed a significant correlation (P < .05) with the absolute volume and percentage volume of the ipsilateral lung spared of ≥20 Gy (55 cc; 7%) and spared of ≥30 Gy (200 cc; 23%). Dosimetric variables of the contralateral lung, total lung, and heart did not show a correlation with incidence of grade ≥3 RP.

Conclusions: In our cohort, sparing the ipsilateral lung of at least 55 cc of 20 Gy and 200 cc of 30 Gy correlated with a reduced incidence of severe (grade ≥3) RP.

Copyright © 2019 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

In plain English

This retrospective study looked at 40 patients with malignant pleural mesothelioma at the authors' institution between December 2010 and October 2016. All had surgery that removes the lining of the lung (pleurectomy/decortication), followed by radiation to one side of the chest using volumetric modulated arc therapy. It was not a study of asbestos, though asbestos histories were recorded. The authors compared dose measurements with whether patients developed severe (grade 3 or higher) radiation pneumonitis, a lung inflammation caused by radiation. Five of the 40 patients (12.5%) did, including one patient whose death was presumed due to pneumonitis. Severe pneumonitis was more common when less of the lung on the treated side was kept below 20 Gy or 30 Gy. It occurred in 4 of 11 patients (36.4%) with under 55 cc spared from 20 Gy, against 1 of 29 (3.4%) with at least 55 cc spared. Doses to the other lung, total lung and heart showed no statistically significant difference. The authors concluded that sparing these volumes correlated with a lower rate of severe pneumonitis, and said prospective studies are needed to validate this.

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 single-institution analysis of radiation dose measurements and lung toxicity
• Who was studied: 49 patients with pathologically proven malignant pleural mesothelioma treated December 2010 to October 2016 were evaluated. 40 met the eligibility criteria (pleurectomy/decortication plus adjuvant hemithoracic radiation at the authors' institution, Icahn School of Medicine at Mount Sinai, New York). 26 were male and 14 female, with a median age of 66.5 years (range 44-84). Median follow-up was 12.5 months.
• Exposure: Adjuvant radiation therapy to one side of the chest using volumetric modulated arc therapy, given to a median dose of 4500 cGy (45 Gy). The study analyzed radiation dose to the lung on the treated side (ipsilateral), the other lung (contralateral), the total lung and the heart. No asbestos fiber types or exposure measurements are given.
• Main results:
  • 7 patients (17.5%) had radiation pneumonitis of grade 2 or higher. Of these, 4 had grade 3 and 1 had presumed fatal (grade 5) pneumonitis, so 5 of 40 patients (12.5%) had grade 3 or higher.
  • Patients with grade 3 or higher pneumonitis differed with statistical significance from those without it in the volume of ipsilateral lung spared of 20 Gy and of 30 Gy. This held for both absolute and percentage volume. There was no significant difference at 40 Gy.
  • The optimal threshold volumes of ipsilateral lung to be spared were calculated as 55 cc for 20 Gy (P = .02) and 200 cc for 30 Gy (P = .04).
  • Among 11 patients with less than 55 cc of ipsilateral lung spared of 20 Gy, 4 developed radiation pneumonitis (36.4%).
  • Among 29 patients with at least 55 cc of ipsilateral lung spared, 1 developed radiation pneumonitis (3.4%).
  • Radiation pneumonitis rates were 50% for patients with less than 200 cc of ipsilateral lung spared (of 30 Gy) and 3.4% for those with more than 200 cc spared.
  • No differences were found for dose to the contralateral lung, total lung, mean lung dose, mean heart dose, or amount of heart overlapping the planning target volume.
  • Asbestos exposure history was recorded for 36 patients: 13 reported known exposure, 11 possible exposure, 9 denied exposure and 4 did not know.
• The authors' conclusion: The authors concluded that sparing at least 55 cc of the ipsilateral lung from 20 Gy and 200 cc from 30 Gy correlated with a reduced incidence of severe radiation pneumonitis. They stated that they have adopted the 200 cc at 30 Gy constraint in their own treatment planning.
• Limitations the authors state:
  • The proposed constraint needs validation in prospective studies.
  • A link between pneumonitis and dose to the other lung could exist but may not have been seen because that dose was low in all patients.
  • Percentage lung volumes may vary depending on how the lung is outlined (contoured) in planning.

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: Pleural Mesothelioma, Pneumonitis.

Related studies

• 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)
• Dosimetric Comparison Between Helical Tomotherapy and Volumetric Modulated Arc Therapy in Patients With Malignant Pleural Mesothelioma — T. Müdder, G.R. Sarria, et al. (2022)
• Tomotherapy after pleurectomy/decortication or biopsy for malignant pleural mesothelioma allows the delivery of high dose of radiation in patients with intact lung — E. Minatel, M. Trovo, et al. (2012)
• Current readings: improvements in intensity-modulated radiation therapy for malignant pleural mesothelioma — K.E. Rosenzweig (2013)
• Intensity modulated radiation therapy after extra-pleural pneumonectomy for malignant pleural mesothelioma is feasible without fatal pulmonary toxicity and provides good survival — S. Jhavar, J. Pruszynski, et al. (2018)
• 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)

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