Imaging in pleural mesothelioma: A review of the 12th International Conference of the International Mesothelioma Interest Group

Our plain-English summary of Imaging in pleural mesothelioma: A review of the 12th International Conference of the International Mesothelioma Interest Group, by S.G. Armato, J. Coolen, A.K. Nowak, et al (Lung Cancer, 2015).

The study

• Authors: S.G. Armato, J. Coolen, A.K. Nowak, C. Robinson, R.R. Gill, C. Straus, A. Khanwalkar
• Journal: Lung Cancer
• Published: 2015;90(2):148-54
• Type of article: Review
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Imaging of malignant pleural mesothelioma is essential to patient management, prognostication, and response assessment. From animal models to clinical trials, the gamut of research activities and clinical standards relies on imaging to provide information on lesion morphology and the growing number of physiologic characteristics amenable to capture through imaging techniques. The complex morphology, growth pattern, and biological mechanisms of mesothelioma, however, present challenges for image acquisition and interpretation. Nevertheless, novel approaches to image acquisition and subsequent image analysis have expanded the opportunities for (as well as the need for) imaging in this disease. This paper summarizes the imaging-based research presented orally at the 2014 International Conference of the International Mesothelioma Interest Group (iMig) in Cape Town, South Africa, October 2014. Presented topics include the imaging of hypoxia in a murine model through positron emission tomography (PET), the use of diffusion-weighted magnetic resonance imaging (MRI) to assess the histologic composition of biphasic mesothelioma and to assess early response to chemotherapy, the correlation of CT-based tumor volume with the volume of the post-surgical tumor specimen, the development of volumetric tumor response criteria, and pre-treatment tumor volume growth considerations for tumor response assessment.

Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

In plain English

This article is a review, not a single study. The authors summarized imaging research on malignant pleural mesothelioma presented orally at the 2014 International Mesothelioma Interest Group conference in Cape Town, South Africa. In mice implanted with mesothelioma tumor cells, a PET tracer for low-oxygen (hypoxic) tissue showed reliable hypoxia in tumors 7 to 10 mm across. In 18 patients with biphasic mesothelioma, a threshold on an MRI measure called ADC identified the dominant tissue type with 83% accuracy, misclassifying three patients. In 14 patients given chemotherapy, MRI tumor volume and ADC values after one month differed significantly between longer and shorter survivors. In 28 surgical patients, the r-squared value between CT tumor volume and the volume of the removed tumor was 0.66. It fell to 0.18 without the four largest tumors. Among 70 patients, volume cut-offs of a 17% decrease and a 58% increase best matched survival. In 17 patients, median tumor growth rate fell from 1.61 before treatment to minus 0.46 during treatment. The authors concluded that PET and MRI remain under investigation and that CT tumor volume needs validation.

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: Review summarizing imaging research presented orally at a scientific conference; it covers one animal experiment and several small patient studies
• Who was studied: The presentations covered the following groups:
• mice (BALB/c) implanted with AB1 mesothelioma cells
• 18 patients with biphasic malignant pleural mesothelioma
• 14 patients with inoperable (stage III and IV) disease given chemotherapy
• 28 patients who had pleurectomy/decortication
• 70 patients with 275 CT scans who had standard chemotherapy
• 17 patients treated at one institution
• Main results:
  • Mouse model: mild hypoxia tracer (F-MISO) activity was seen in tumors of 5 to 7 mm, and reliable hypoxia in tumors of 7 to 10 mm.
  • Mouse model, preliminary results: nitroglycerine visually reduced tracer intensity compared with untreated mice.
  • Mouse model: hyperbaric oxygen gave a reduction of borderline statistical significance, and tirapazamine gave no significant change.
  • 18 biphasic mesothelioma patients (12 epithelioid-dominant, 6 sarcomatoid-dominant): the optimal ADC threshold (1.025 times 10 to the minus 3 mm2/s) misclassified three patients, giving 83% accuracy. Sarcomatoid-dominant tumors had lower ADC values.
  • 14 chemotherapy patients: several tumor volume and ADC measures at 1 month differed significantly between long-term and short-term overall survival groups (p = 0.01 to 0.04). Smaller tumor volume and higher ADC went with longer survival.
  • 28 surgical patients: the r-squared value between CT-based tumor volume and gross tumor specimen volume was 0.66. Leaving out the four cases with specimen volume over 1000 ml, it was 0.18.
  • 70 patients (275 CT scans): a tumor volume decrease of at least 17% and an increase of at least 58% were the response cut-offs most closely linked to survival.
  • Same 70 patients: these cut-offs gave a C statistic of 0.76, compared with 0.61 for criteria extrapolated directly from RECIST.
  • 17 patients: 14 of 17 (82.4%) were classified as stable disease by RECIST. Median tumor volume growth rate was 1.61 before treatment and minus 0.46 during treatment (p = 0.0005).
• The authors' conclusion: The authors concluded that, although CT remains standard, PET and MRI are under continued investigation for assessing tumor function and composition. They also concluded that CT-derived tumor volume must be validated against a reliable reference standard.
• Limitations the authors state:
  • The diffusion-weighted MRI outcome data are preliminary and need confirmation in larger patient groups.
  • The ADC threshold for biphasic tumors still needs a future prospective validation study.
  • The survival cut-offs in the MRI study came from a small study.
  • Measuring mesothelioma volume from images is not straightforward.
  • The volumetric response criteria require validation before clinical use.
  • Future studies must test whether the growth-rate approach better predicts survival.

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, Mesothelioma, Clinical Trial, IMIG, Hypoxia, Biphasic Mesothelioma, Chemotherapy.

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