Establishing locoregional control of malignant pleural mesothelioma using high-dose radiotherapy and (18) F-FDG PET/CT scan correlation

Our plain-English summary of Establishing locoregional control of malignant pleural mesothelioma using high-dose radiotherapy and (18) F-FDG PET/CT scan correlation, by M. Feigen, S.T. Lee, C. Lawford, et al (Journal of Medical Imaging and Radiation Oncology, 2011).

The study

• Authors: M. Feigen, S.T. Lee, C. Lawford, K. Churcher, E. Zupan, A.M. Scott, C. Hamilton
• Journal: Journal of Medical Imaging and Radiation Oncology
• Published: 2011;55(3):320-32
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: The management of malignant pleural mesothelioma represents one of the most challenging issues in oncology, as there is no proven long-term benefit from surgery, radiotherapy or chemotherapy alone or in combination. Locoregional progression remains the major cause of death, but radical surgical resection may produce major postoperative morbidity. While radical or postoperative radiotherapy using conventional techniques has resulted in severe toxicity with no impact on survival, recent advances in radiotherapy delivery may be more effective.

Methods: We treated patients with locally advanced mesothelioma whose tumours had been sub optimally resected with high-dose three-dimensional conformal radiotherapy (3DCRT) or intensity-modulated radiotherapy (IMRT) to large volumes of one hemithorax, using CT and positron emission tomography (PET) scan-based treatment planning. Clinical outcomes were assessed by determining patterns of failure and metabolic changes in total glycolytic volume (TGV) between pre- and post-irradiation( 18) F-FDG PET/CT scans and by recording acute and late toxicity grades.

Results: Fourteen patients were analysed with 40 PET scans performed before and up to 4.5years after radiotherapy. Eleven patients had pleurectomy/decortications, one had an extrapleural pneumonectomy and two had no surgery. Four patients who received chemotherapy had all progressed prior to radiotherapy. After radiotherapy, the in-field local control rate was 71%. No progression occurred in two patients, one was salvaged with further radiotherapy to a new site, four recurred inside the irradiated volume all with concurrent distant metastases and the other seven had distant metastases only. The TGVs were reduced by an average of 67% (range 12-100%) after doses of 45 to 60Gy to part or all of one hemithorax. There were no serious treatment-related toxicities. Median survival was 25months from diagnosis and 17months after starting radiotherapy.

Conclusions: We have established that mesothelioma can be locally controlled with high radiation doses using 3DCRT or IMRT, and that strict normal tissue dose constraints have limited radiation toxicities. Radiotherapy should be considered to prevent or delay the local manifestations of progressive disease in suitable patients after surgery including extrapleural pneumonectomy and pleurectomy/decortication. Higher radiation doses may allow more effective palliation.

© 2011 The Authors. Journal of Medical Imaging and Radiation Oncology © 2011 The Royal Australian and New Zealand College of Radiologists.

In plain English

This study reported on 14 consecutive patients with malignant pleural mesothelioma, all previously exposed to asbestos, who were treated with high-dose radiotherapy to one side of the chest in Melbourne, Australia, between July 2003 and July 2009. Seven other patients seen in that period were not analysed because they had no follow-up PET scans. Eleven of the 14 had undergone pleurectomy/decortication, one an extrapleural pneumonectomy and two no surgery. Doses were 45 to 60 Gy. Disease did not return inside the treated area in 10 of 14 (71%). Two had no recurrence anywhere, and eight recurred only outside the treated area. In the 10 patients whose scans could be assessed, total glycolytic volume, a PET measure combining tumour size and activity, fell by an average of 67%. No grade 4 or 5 acute and no late side effects were recorded. Grade 3 effects did occur, including liver dysfunction in two patients and pneumonitis in two. Median survival was 28 months from diagnosis and 17 months from the start of radiotherapy. The authors concluded that mesothelioma can be locally controlled with these doses and called for a randomised trial. They noted limits of PET, including telling radiation lung inflammation apart from tumour.

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: Single-institution treatment series (protocol of high-dose palliative radiotherapy) with prospective data collection and comparison of PET scans before and after treatment; no comparison group
• Who was studied: 14 consecutive patients with malignant pleural mesothelioma who had follow-up PET/CT scans, treated at Austin Health, Melbourne, Australia, July 2003 to July 2009. There were 12 males and 2 females aged 37 to 72 years (median 62), all with prior asbestos exposure. Histology was epithelioid in 10, biphasic in 3 and desmoplastic in 1. Seven other patients seen in this period were not analysed because they had no follow-up PET scans.
• Exposure: Radiotherapy of 45 to 60 Gy in 1.8 to 2.0 Gy fractions to part or all of one hemithorax, using three-dimensional conformal radiotherapy (9 patients) or IMRT (5 patients). Eleven patients had prior pleurectomy/decortication, one extrapleural pneumonectomy and two no surgery. All patients had prior asbestos exposure; no fiber types are given.
• Main results:
  • Seven patients seen during the study period were not analysed because they had no follow-up PET scans.
  • The in-field local control rate was 71% (10 of 14 patients), based on CT and PET/CT scans.
  • Two of the 14 patients (14%) had no recurrence at any site. Eight of the remaining 12 had recurrence only outside the planning target volume.
  • All four patients whose disease recurred inside the treated area had stage IV disease and also had relapses outside the irradiated volume.
  • Total glycolytic volume (TGV), a composite of tumour metabolic activity and volume on PET, could not be assessed in 4 patients. In the other 10 it fell by a mean of 67%, ranging from 11.6% to 99.5%. Among the nine patients with assessable scans within 6 months, the average reduction was 47%.
  • No acute grade 4 or 5 radiation toxicities were seen, toxicities were transient and no late toxicities occurred.
  • Grade 3 effects were recorded. Two patients had grade 3 liver dysfunction on liver function tests.
  • Two patients had grade 3 pneumonitis (Table 4). One patient had grade 3 dyspnoea and pneumonitis requiring steroids.
  • Median survival of all 14 patients was 28 months from diagnosis (range 10 to 79 months) and 17 months from the start of radiotherapy (range 6 to 72 months).
  • Four of the 14 patients were alive 17 to 72 months after starting radiotherapy. Nine died of progressive mesothelioma, typically outside the irradiated volumes, and one died of a second malignancy (melanoma).
• The authors' conclusion: The authors concluded that mesothelioma is a radio-responsive disease that can be locally controlled with doses of 45 to 60 Gy, and that radiotherapy should be assessed in a randomised trial as part of multimodality programmes after surgery.
• Limitations the authors state:
  • Limits of PET technology: lesions below the scanner's 10-mm resolution may be missed, and FDG uptake from radiation pneumonitis, postoperative changes, infection or normal tissue may be falsely positive.
  • In four cases, possible non-cancer changes on the scans could not be resolved, likely because of unresolved radiation pneumonitis.
  • Staging based on PET differed substantially from staging based on pathology.
  • Few scans were done beyond 12 months (nine scans in five patients), and relapse was confirmed by histology in only two cases.

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, CT Scan, Chemotherapy, Surgical Resection, Mesothelioma, Intensity-Modulated Radiation Therapy (IMRT), Hemithorax, PET Scan.

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