Clinical implications of 18F-fluorodeoxyglucose positron emission tomography/computed tomography at delayed phase for diagnosis and prognosis of malignant pleural mesothelioma

Our plain-English summary of Clinical implications of 18F-fluorodeoxyglucose positron emission tomography/computed tomography at delayed phase for diagnosis and prognosis of malignant pleural mesothelioma, by Y. Abe, K. Tamura, I. Sakata, et al (Oncology Reports, 2012).

The study

• Authors: Y. Abe, K. Tamura, I. Sakata, J. Ishida, Y. Ozeki, A. Tamura, K. Uematsu, H. Sakai, T. Goya, M. Kanazawa, K. Machida
• Journal: Oncology Reports
• Published: 2012;27(2):333-8
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma (MPM) has a poor prognosis, and conventional imaging modalities do not reflect the prognosis of MPM. In this study, the clinical significance of 18F-fluorodeoxyglucose positron emission tomography/computed tomography fusion imaging (18F-FDG PET/CT) was evaluated for the differential diagnosis, staging and prognosis in MPM patients. Ninety patients who underwent 18F-FDG PET/CT scanning due to a clinical diagnosis or suspicion of MPM prior to therapy were reviewed. Of 90 patients, 31 were pathologically diagnosed as MPM. Maximum standardized uptake values (SUVmax) were semi-quantitatively obtained from PET/CT 60 min (early phase) and 120 min (delayed phase) after injection of 18F-FDG, and the clinicopathological correlations with the level of SUVmax obtained from PET/CT were examined. The survival curves of MPM patients were plotted according to the methods of Kaplan-Meier. The prognostic implications of the level of SUVmax were estimated by t-test. PET/CT scan showed intense abnormal FDG uptake (SUVmax>2.0) in the pleural lesions of all 31 MPM patients at delayed phase, while it showed abnormal FDG uptake in 30 (97%) patients at early phase. In all 31 MPM patients, the values of SUVmax at delayed phase were higher than those at the early phase. PET/CT also indicated metastasis in the lymph node in 7 patients (23%) and in the systemic lesions in 8 patients (26%) with MPM. Twenty-three MPM patients with high SUVmax, whose prognosis was apparent, showed significantly poorer prognosis in both early and delayed phase (respectively, p=0.03 and p=0.01, t-test). The results showed that 18F-FDG PET/CT at delayed phase is very useful for the diagnosis of pleural diseases, and SUVmax on PET/CT in the delayed phase is a more reliable prognostic factor than that in the early phase. High uptake of 18F-FDG PET/CT may be a predictive factor of prognosis in MPM patients.

In plain English

This Japanese study reviewed 90 patients scanned with FDG PET/CT, an imaging test of sugar uptake by tissues, at one clinic between August 2005 and July 2010 because malignant pleural mesothelioma (MPM) was diagnosed or suspected. Uptake (SUVmax) was measured 60 minutes (early phase) and 120 minutes (delayed phase) after injection. Pathology confirmed MPM in 31 patients, 20 of whom had noted asbestos exposure. With a cut-off of SUVmax above 2.0, sensitivity was 97% early and 100% delayed, and specificity was 88% at both phases. Seven patients without MPM also showed high uptake, including some with tuberculous pleuritis or inflammatory diseases. Uptake was not significantly related to age, gender, asbestos exposure or smoking. Among 23 MPM patients with known outcome, those with higher uptake had significantly poorer prognoses (early phase p=0.03; delayed phase p=0.01). The authors concluded that delayed-phase scanning gives more useful diagnostic information and that its uptake value is a more reliable prognostic factor. They noted that only some metastases were confirmed by pathology.

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: Retrospective review of patients' PET/CT scans (diagnostic imaging study) at a single clinic
• Who was studied: 90 patients with clinically diagnosed or suspected malignant pleural mesothelioma, scanned before initial therapy at Tokorozawa PET Diagnostic Imaging Clinic, Japan, between August 2005 and July 2010. 31 were pathologically diagnosed with MPM: 12 before PET/CT and 19 after. The 31 MPM patients were 27 males and 4 females, with a mean age of 67 years (range 47-79).
• Exposure: The study examined 18F-FDG PET/CT uptake (SUVmax) at early (60 min) and delayed (120 min) phase, not asbestos exposure. Asbestos exposure history was recorded: noted in 20 of 31 MPM patients, with no apparent exposure in 11. No fiber types or jobs were given.
• Main results:
  • Among the 31 MPM patients, intense abnormal FDG uptake (SUVmax above 2.0) was seen in all 31 at delayed phase and in 30 (97%) at early phase.
  • For the 90 patients, sensitivity was 97% at early phase and 100% at delayed phase. Specificity was 88% at both phases.
  • Seven patients with suspected MPM who had high delayed-phase uptake were diagnosed with other conditions: 2 tuberculous pleuritis, 1 pleuritis carcinomatosa and 4 non-specific inflammatory diseases.
  • In all 31 MPM patients, SUVmax was higher at delayed phase (range 2.2-16.2, mean 7.5) than at early phase (range 1.7-13.5, mean 6.1).
  • In MPM patients, SUVmax was not significantly related to age, gender, asbestos exposure or smoking.
  • PET/CT indicated lymph node metastasis in 7 MPM patients (23%) and systemic metastasis in 8 (26%).
  • SUVmax was lower in the 14 epithelioid MPM patients than in the 12 non-epithelioid patients at both phases, but the difference was not significant.
  • Among 23 MPM patients whose prognosis was known, at early phase the 16 with SUVmax above 3.65 had significantly poorer prognoses than the 7 with lower values (p=0.03, t-test).
  • At delayed phase, the 12 MPM patients with SUVmax above 6.0 had significantly poorer prognoses than the other 11 (p=0.01, t-test). The authors reported no significant difference in therapy between the high- and low-SUVmax groups.
• The authors' conclusion: The authors concluded that delayed-phase PET/CT gives more useful information for the differential diagnosis of pleural diseases. They also concluded that high FDG uptake may be a predictive factor of prognosis in MPM patients, and that delayed-phase SUVmax is a more reliable prognostic factor than early-phase SUVmax.
• Limitations the authors state:
  • There was only one surgical case, and pathological diagnosis of metastasis was insufficient to evaluate staging of MPM by PET/CT.
  • Only some of the metastatic lesions were confirmed by pathology.
  • There were false positives: PET/CT showed intense uptake in inflammatory diseases and pleuritis carcinomatosa as well as in MPM.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Prognosis, Pleural Mesothelioma, Differential Diagnosis, Staging, CT Scan, Metastasis.

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