Proton Therapy for Malignant Pleural Mesothelioma: A Three Case Series Describing the Clinical and Dosimetric Advantages of Proton-Based Therapy

Our plain-English summary of Proton Therapy for Malignant Pleural Mesothelioma: A Three Case Series Describing the Clinical and Dosimetric Advantages of Proton-Based Therapy, by H. Lee, J. Zeng, S.R. Bowen, et al (Curēus, 2017).

The study

• Authors: H. Lee, J. Zeng, S.R. Bowen, R. Rengan
• Journal: Curēus
• Published: 2017;9(9):e1705
• Type of article: Case report
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant pleural mesothelioma (MPM) is a malignancy of the pleural cavity that typically presents at an advanced stage. Due to its large, circumferential clinical target volume (CTV) and proximity to major structures, including the heart and contralateral lung, delivering hemithoracic intensity-modulated radiotherapy (IMRT) with photon therapy to achieve loco-regional control following macroscopic complete resection is challenging. Intensity-modulated proton therapy (IMPT) has been shown to be a method for achieving higher therapeutic doses while limiting exposure to organs at risk (OARs), but patient outcomes after treatment have yet to be reported. We present three patients who received IMPT to 54 Gy after extrapleural pneumonectomy (EPP), with two patients receiving boosts to 66 and 60 Gy. All three tolerated treatment well and received doses to OARs markedly lower than those seen in comparison volumetric-modulated arc therapy (VMAT) IMRT photon plans. Radiation pneumonitis, a highly morbid and potentially fatal toxicity in patients receiving thoracic radiotherapy, was not observed even with boost treatments. In practice, IMPT appears to match dosimetric predictions as a feasible and safer alternative to photon IMRT-based radiotherapy.

In plain English

This case series described three men, aged 71, 47 and 46, with malignant pleural mesothelioma. Each had cisplatin/pemetrexed chemotherapy and extrapleural pneumonectomy surgery, then intensity-modulated proton therapy to 54 Gy. Two also received boosts, to 66 and 60 Gy. Asbestos exposure is not discussed. Each proton plan was compared with a photon (VMAT) plan made for the same patient. With protons, mean opposite-lung doses were 1.53, 0.74 and 0.26 Gy. No radiation pneumonitis was observed, though the authors said Patient Three's cough could have been subacute radiation pneumonitis; they favored other causes. For Patient One, 8.45% of the opposite lung received above 5 Gy with protons, versus 78.2% in the photon plan. The worst side effects reported were grade two, such as nausea and skin inflammation. Patient One's cancer recurred; he died 25 months after radiation. Patient Two had distant recurrence and died four months after radiation. Patient Three had no radiographic evidence of progression at 14 months. The authors concluded that doses up to 66 Gy appear feasible and safe. They noted the small numbers and short follow-up.

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: case series (three patients), with comparison of proton treatment plans against photon VMAT plans generated for the same patients
• Who was studied: Three men (aged 71, 47 and 46) with malignant pleural mesothelioma (stage III biphasic, stage IV epithelioid, stage III epithelioid), treated after right-sided extrapleural pneumonectomy; place and dates of treatment not stated
• Exposure: Not an asbestos exposure study. The treatment studied was intensity-modulated proton therapy to 54 Gy after neoadjuvant cisplatin/pemetrexed and extrapleural pneumonectomy, with boosts to 66 Gy and 60 Gy in two patients
• Main results:
  • Mean doses to the contralateral (opposite) lung with proton therapy were 1.53, 0.74 and 0.26 Gy in the three patients, and the authors reported no development of radiation pneumonitis
  • The authors said Patient Three's cough, which resolved by eight months, could have been subacute radiation pneumonitis, but they favored other causes because he had no fevers or radiographic findings
  • For Patient One, the volume of contralateral lung receiving above 5 Gy was 8.45% in the proton plan versus 78.2% in the comparison photon VMAT plan
  • Patients completed treatment without breaks. The most significant adverse effects in Patient One were grade two nausea and dermatitis
  • Patient One had recurrence, entered hospice and died 25 months after radiation
  • Patient Two had distant recurrences on a CT scan three months after radiation and died four months after radiation
  • Patient Three was 14 months after radiation with no radiographic evidence of progression at the time of reporting
• The authors' conclusion: The authors concluded that, based on a maximum follow-up of 25 months and a median of 14 months, proton doses of up to 66 Gy appear feasible and safe, with lower doses to organs at risk than in photon plans
• Limitations the authors state:
  • Small number of patients and relatively short follow-up
  • No survival comparison with larger published series was possible

Topics

Medical terms in this study, explained in our Lexicon: Proton Therapy, Pleural Mesothelioma, Pleural Cavity, Intensity-Modulated Radiation Therapy (IMRT), Extrapleural Pneumonectomy (EPP), Pneumonitis.

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• Dosimetric Comparison of Lung-Sparing Radiation Therapy between Volumetric Arc Therapy and Helical Tomotherapy for Unresectable Malignant Pleural Mesothelioma — B. Pehlivan, K. Sengul, et al. (2019)
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