Current evidence base of FDG-PET/CT imaging in the clinical management of malignant pleural mesothelioma: emerging significance of image segmentation and global disease assessment

Our plain-English summary of Current evidence base of FDG-PET/CT imaging in the clinical management of malignant pleural mesothelioma: emerging significance of image segmentation and global disease assessment, by S. Basu, B. Saboury, D.A. Torigian, et al (Molecular Imaging and Biology, 2011).

The study

• Authors: S. Basu, B. Saboury, D.A. Torigian, A. Alavi
• Journal: Molecular Imaging and Biology
• Published: 2011;13(5):801-11
• Type of article: Review
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Increasingly, integrated positron emission tomography-computed tomography (PET/CT) imaging is playing a crucial role in the assessment of patients with known or suspected malignant pleural mesothelioma (MPM). Based on the data reported in the literature, this combined modality is likely to become the instrument of choice for examining patients of MPM. The research on this subject has focused on the following five domains: (1) differentiation of MPM from other benign pleural diseases, (2) preoperative staging for the selection of appropriate candidates for surgery, (3) evaluation for therapy response and post-treatment surveillance for recurrence, (4) prognostication based upon the intensity of 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) uptake, and (5) planning of radiotherapy. These represent the bases for critical decision making in the management of mesothelioma, and FDG-PET/CT offers potential advantages over conventional CT imaging and thus can play a pivotal role in this regard. Optimal characterization of this potentially fatal disease with a high negative predictive value for MPM, superior capability for cancer staging initially and at the later course of disease, and ability for measuring therapeutic response and the precise determination of the target volume for radiotherapy planning represent distinct advantages of this promising molecular imaging tool. In this communication, we have explored the promising role of integrated FDG-PET/CT in the overall management of this serious malignancy. From the available data, the major role of PET-CT at present appears to be in the preoperative disease staging, response to treatment assessment, and post-treatment disease surveillance of MPM. In all these three areas, PET-CT convincingly shows better results than conventional anatomical imaging alone and thereby can aid in exploring novel therapeutic approaches. Disease prognosis and radiotherapy planning are evolving areas where this modality has demonstrated significant promise, but this has to be investigated further. The differentiating of MPM from benign pleural disease is a challenging issue; though in limited studies, it has shown promising results, single standardized uptake value (SUV) cutoff technique cannot be the optimal way for this purpose. Dual time point and delayed imaging helps further in this setting; however, more data require to be accrued in this area. We, in this review, have also discussed the feasibility of a new method of image segmentation based on an iterative thresholding algorithm, which permits definition of the boundaries of lesions based on PET images alone to provide lesional metabolically active tumor volumes, lesional partial volume corrected SUV (PVC-SUV) measurements, lesional PVC metabolic burden (PVC-MB) (calculated as the product of lesional MVP and lesional PVC-SUV), and whole body metabolic burden (WBMB) (calculated as the sum of lesional PVC-MB of all lesions). This global disease assessment, we believe, will be the way forward for assessing this malignancy with a non-invasive imaging modality.

In plain English

This article was a review, not a new study. The authors searched Medline and PubMed for English-language papers on FDG-PET/CT scanning in malignant pleural mesothelioma, giving most weight to studies of at least 15 patients. They summarized other researchers' findings on five uses of the scan: telling mesothelioma apart from benign pleural disease, staging before surgery, checking response to treatment and recurrence, predicting survival, and planning radiotherapy. In one reviewed study of 31 patients (17 with mesothelioma, 14 with benign pleural disease), an SUV cutoff of 2.2 gave 94.1% sensitivity and 100% specificity. In a study of 35 patients, PET/CT excluded 14 of the 35 from surgery. In a study of 42 patients, PET/CT avoided non-curative surgery in 29%. In another, standard SUV response measures were not related to survival, while tumor glycolysis and volume measures were. The authors also described their own group's scan-analysis method and called preliminary images feasible. The authors concluded that PET/CT appears to give superior staging and better monitoring of treatment response. They noted that data on newer tracers were limited. The review did not study asbestos exposure.

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: Narrative review of published studies (literature search of Medline and PubMed)
• Who was studied: Published English-language studies of PET/CT in malignant pleural mesothelioma. Studies with at least 15 patients were emphasized, plus one radiotherapy-planning study of 13 patients. No publication-date limit was used.
• Exposure: Not an asbestos exposure study. The subject was FDG-PET/CT imaging, compared with conventional imaging such as contrast-enhanced CT and MRI. Asbestos is mentioned only in background on rising incidence.
• Main results:
  • Yildirim et al. (31 patients, differentiating mesothelioma from asbestos-related benign pleural disease): an SUV cutoff of 2.2 gave 94.1% sensitivity, 100% specificity, 100% positive predictive value and 93.3% negative predictive value
  • In the same Yildirim study, the group sizes were 17 patients with mesothelioma and 14 with benign pleural disease. PET/CT correctly detected malignancy in 15 of the 17 and correctly identified 13 of the 14 benign cases.
  • Orki et al. (83 patients, benign versus malignant pleural disease): PET/CT had 100% sensitivity, 94.8% specificity and 97.5% accuracy; false positives were due to pleural tuberculosis
  • Wilcox et al. (35 patients with proven mesothelioma): PET/CT excluded 14 of 35 from surgery. Median survival was 20 months for patients who had extrapleural pneumonectomy and 12 months for those excluded from surgery by PET/CT.
  • Sorensen et al. (42 mesothelioma patients): non-curative surgery was avoided in 29% by preoperative PET/CT and in a further 14% by mediastinoscopy
  • Tan et al. (44 patients, scanned after multimodality therapy when recurrence was suspected): PET/CT had 94% sensitivity, 100% specificity, 100% positive predictive value and 88% negative predictive value for recurrence
  • Veit-Haibach et al. (41 patients, response to therapy): changes in SUVmax and SUVmean were not related to survival, but decreases in tumor lesion glycolysis and PET volume were predictive
  • Pehlivan et al. (13 patients, radiotherapy planning): in 12 of 13 patients, PET/CT-based outlining reduced target volumes compared with CT. Mean gross tumor volume fell by 47.1±28.4%.
  • A dual time point study (44 patients with mesothelioma, 11 with benign pleural disease): FDG uptake increased over time in pleural malignancy and stayed stable or decreased in benign disease
  • The authors' own group described an image-segmentation method for measuring whole-body metabolic burden. They presented preliminary images (one 78-year-old male patient in Fig. 1) as showing feasibility.
• The authors' conclusion: The authors concluded that combined PET/CT in mesothelioma appears to provide superior disease staging at diagnosis and later, better monitoring of treatment response, and accurate target volumes for radiotherapy planning.
• Limitations the authors state:
  • Benchmarks for judging response to novel therapies on PET have not been well defined
  • Data on newer PET tracers in mesothelioma are limited and come mainly from animal studies
  • Inflammation after surgery or talc pleurodesis can cause non-specific FDG uptake that confounds interpretation

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, Staging, Mesothelioma, PET-CT, Prognosis.

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