Intensity-modulated radiotherapy and volumetric-modulated arc therapy for malignant pleural mesothelioma after extrapleural pleuropneumonectomy

Our plain-English summary of Intensity-modulated radiotherapy and volumetric-modulated arc therapy for malignant pleural mesothelioma after extrapleural pleuropneumonectomy, by J. Krayenbuehl, O. Riesterer, S. Graydon, et al (Journal of Applied Clinical Medical Physics, 2013).

The study

• Authors: J. Krayenbuehl, O. Riesterer, S. Graydon, P. Dimmerling, S. Kloeck, I.F. Ciernik
• Journal: Journal of Applied Clinical Medical Physics
• Published: 2013;14(4):4130
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Radiotherapy reduces the local relapse rate after pleuropneumonectomy of malignant pleural mesothelioma (MPM). The optimal treatment technique with photons remains undefined. Comparative planning for intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) was performed. Six MPM patients with significant postoperative intrathoracic air cavities were planned with IMRT and VMAT. A dose comparison for the targets and organ at risks (OAR) was performed. Robustness was assessed in respect to the variation of target dose with change in volume of air cavities. VMAT reduced the dose to the contralateral lung by reducing the volume covered by 13 Gy and 20 Gy by a factor 1.8 and 2.8, in respect to IMRT (p = 0.02). Dose distribution with VMAT was the most stable technique in regard to postsurgical air cavity variation. For IMRT, V90, V95, and the minimal target dose decreased by 40%, 64%, and 12% compared to 29%, 47%, and 7% with VMAT when air cavity decreased. Two arcs compared to one arc decreased the dose to all the organs at risk (OAR) while leaving PTV dose coverage unchanged. Increasing the number of arcs from two to three did not reduce the dose to the OAR further, but increased the beam-on time by 50%. Using partial arcs decreased the beam-on time by 43%. VMAT allows a lower lung dose and is less affected by the air cavity variation than IMRT. The best VMAT plans were obtained with two partial arcs. VMAT seems currently the most suitable technique for the treatment of MPM patients when air cavities are remaining and no adaptive radiotherapy is performed.

In plain English

This was a radiation treatment-planning study, not a study of asbestos exposure or of patient outcomes. It compared calculated doses from two techniques for malignant pleural mesothelioma after extrapleural pleuropneumonectomy, surgery that removes the lung and pleura. At Zurich University Hospital, 16 patients were treated between 2004 and 2011. The six whose chest cavity still held more than 100 cm3 of air were each planned with intensity-modulated radiotherapy (IMRT) and with volumetric-modulated arc therapy (VMAT). Tumor-target coverage did not differ significantly between the two. With VMAT, a smaller share of the remaining lung received 13 Gy (3.3% versus 6.1% with IMRT) and 20 Gy (0.9% versus 2.5%), p = 0.02 for both. VMAT took about 4 minutes rather than about 10. When the air cavity shrank, target dose fell more with IMRT. In one patient, two partial arcs worked best. The authors concluded that VMAT lowers dose to the remaining lung and is less affected by changing air cavities. They recommended close monitoring when the cavity changes by more than 200 cm3.

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: Comparative radiotherapy treatment-planning (dosimetric) study; each patient was planned with both IMRT and VMAT, two prospectively and four retrospectively
• Who was studied: 6 of 16 patients with malignant pleural mesothelioma (MPM) treated with external radiotherapy at Zurich University Hospital, Switzerland, between 2004 and 2011, after preoperative chemotherapy and extrapleural pleuropneumonectomy; selected because postoperative air cavities exceeded 100 cm3 (5 male, 1 female; 5 right-sided, 1 left-sided)
• Exposure: No asbestos exposure was studied. The study compared radiotherapy techniques, IMRT versus VMAT, each delivering 26 × 1.75 Gy (45.5 Gy) to PTV2 with a simultaneous boost of 26 × 2.15 Gy (55.9 Gy) to PTV1. VMAT was also tested with one, two or three partial or full arcs.
• Main results:
  • Target coverage, dose homogeneity, and minimal and maximal dose in PTV1 differed only slightly between IMRT and VMAT, and the differences were not significant.
  • Contralateral lung: V13 was 6.1±1.8% with IMRT and 3.3±1.4% with VMAT. V20 was 2.5±1.2% with IMRT and 0.9±1.1% with VMAT (p = 0.02 for both). Lung V5 was higher with VMAT (40.8% versus 32.4%), and the mean lung dose difference was not significant.
  • The ipsilateral kidney, which is surrounded by the target, could not be kept within its dose objectives with either technique.
  • Monitor units per 2.15 Gy fraction fell from 2080 ± 414 with IMRT to 485 ± 82 with VMAT (p < 0.01).
  • Treatment time was about 10 minutes for IMRT and about 4 minutes for VMAT.
  • As air cavities shrank, the PTV1 volume receiving 90% of the prescribed dose fell by up to 40.3% with IMRT and up to 9.4% with VMAT.
  • As air cavities shrank, the PTV1 volume receiving 95% of the prescribed dose fell by up to 64.4% with IMRT and up to 29.2% with VMAT.
  • As air cavities shrank, the PTV1 minimal dose fell by up to 12.4% with IMRT and up to 6.9% with VMAT.
  • In one patient, chosen because the PTV volume was closest to the mean, two arcs reduced dose to all organs at risk compared with one arc.
  • In the same patient, three arcs gave no further improvement over two.
  • Partial arcs had 43% shorter beam-on time than full arcs.
• The authors' conclusion: The authors concluded that VMAT with multiple partial arcs reduced dose to the remaining lung compared with IMRT and was less susceptible to changing air cavities. They recommended attentive monitoring, with possible replanning, when air cavity variation exceeds 200 cm3.

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: Intensity-Modulated Radiation Therapy (IMRT), Pleural Mesothelioma, Intrathoracic.

Related studies

• Long-term results in malignant pleural mesothelioma treated with neoadjuvant chemotherapy, extrapleural pneumonectomy and intensity-modulated radiotherapy — C. Thieke, N.H. Nicolay, et al. (2015)
• 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)
• Intensity-modulated radiotherapy after extrapleural pneumonectomy in the combined-modality treatment of malignant pleural mesothelioma — A. Chi, Z. Liao, et al. (2011)
• Clinical experience of volumetric modulated arc therapy for malignant pleural mesothelioma after extrapleural pneumonectomy — T. Kimura, Y. Doi, et al. (2015)
• 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)
• Training and validation of a knowledge-based dose-volume histogram predictive model in the optimisation of intensity-modulated proton and volumetric modulated arc photon plans for pleural mesothelioma patients — D. Franceschini, L. Cozzi, et al. (2022)

Browse more research in Journal of Applied Clinical Medical Physics, or return to medical research.