Diagnostic accuracy of sequential co-registered PET+MR in comparison to PET/CT in local thoracic staging of malignant pleural mesothelioma

Our plain-English summary of Diagnostic accuracy of sequential co-registered PET+MR in comparison to PET/CT in local thoracic staging of malignant pleural mesothelioma, by K. Martini, A. Meier, I. Opitz, et al (Lung Cancer, 2016).

The study

• Authors: K. Martini, A. Meier, I. Opitz, W. Weder, P. Veit-Haibach, R.A. Stahel, T. Frauenfelder
• Journal: Lung Cancer
• Published: 2016;94:40-5
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To investigate the diagnostic accuracy of sequential co-registered PET+MR (PET+MR) for local staging of malignant pleural mesothelioma (MPM) compared to PET/CT.

Material And Methods: In a prospective clinical trial 34 consecutive patients (median age 66 years; range 40-79 years; 1 female, 33 male) with known MPM, who underwent PET/CT and PET+MR exams for either staging or re-staging/follow-up were evaluated. Imaging was conducted using a tri-modality PET/CT-MR set-up (Discovery PET/CT 690, 3T Discovery MR 750w, both GE Healthcare, Waukesha, WI, USA). In 26 cases histopathology served as standard of reference. Two independent readers evaluated images for T and N stage, confidence level (sure to unsure; 1-3) and subjective overall image quality (very good to non-diagnostic; 1-4). Inter-observer agreement of T and N stages (Cohen's kappa) and interclass correlation coefficient (ICC) between PET/CT vs. PET+MR was calculated.

Results: Inter observer agreement for evaluation of T and N Stage in PET/CT images was excellent (k=0.844 and k=0.824, respectively), whereas PET+MR imaging showed substantial agreement in T and N stage (k=0.729 and k=0.691, respectively). The ICC of PET/CT vs. PET+MR for evaluation of both, T and N Stage, was excellent (ICC=0.951 and ICC=0.93, respectively). Diagnostic confidence was scored significantly higher in PET+MR compared to PET/CT (mean score=1.66 and 1.93, respectively; p=0.004). Image quality was diagnostic for all image series. Comparing pT and pN stage vs cT and cN stage (n=26 cases), both imaging modalities showed excellent agreement for T stage (ICCPET+MR=0.888 vs. ICCPET/CT=0.853, respectively) and substantial to moderate agreement for N stage (ICCPET+MR=0.683 vs. ICC=0.595PET/CT, respectively).

Conclusion: Our findings suggest that diagnostic accuracy of PET+MR is comparable to PET/CT for local staging of MPM, whereas radiologists felt significantly more confident staging PET+MR compared to PET/CT images (p=0003), using dedicated sequences.

Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

In plain English

This prospective study at University Hospital Zurich compared two scan methods for judging how far malignant pleural mesothelioma had spread in the chest: the tumor itself (T stage) and the lymph nodes (N stage). Thirty-four patients (33 men, 1 woman; median age 66) had both PET/CT and PET+MR scans. Two readers staged every scan independently. For 26 patients, staging from surgically removed tissue served as the reference. The two scan methods agreed closely with each other. Against tissue staging, overall agreement scores for T stage were 0.844 for PET/CT and 0.874 for PET+MR, and for N stage 0.551 and 0.666. Each reader staged T correctly in 17 of 26 patients with either method. All scans were rated good enough to use. The authors reported that readers were significantly more confident with PET+MR (mean 1.66 versus 1.93, p = 0.003), though the article describes its confidence scale inconsistently. The authors concluded that PET+MR's accuracy is comparable to PET/CT for local staging. They noted that tissue results existed for only 26 of 34 patients. The study did not examine 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: Prospective clinical study comparing two imaging methods (PET/CT and sequential co-registered PET+MR), using surgical histopathology as the reference standard where available
• Who was studied: 34 consecutive adult patients (median age 66, range 40 to 79; 33 male, 1 female) referred for staging or re-staging/follow-up of malignant pleural mesothelioma at University Hospital Zurich, Switzerland. Histopathologic staging was available for 26 of them. Study dates are not given.
• Exposure: Not an exposure study. What was compared was imaging: PET/CT versus PET+MR, performed on a tri-modality PET/CT-MRI setup. Asbestos exposure was not measured or analyzed.
• Main results:
  • PET/CT and PET+MR agreed closely with each other, with an intraclass correlation (ICC) of 0.951 for T stage and 0.930 for N stage.
  • Agreement between the two readers was excellent for PET/CT (kappa 0.844 for T stage, 0.824 for N stage) and substantial for PET+MR (kappa 0.729 for T stage, 0.691 for N stage).
  • Against surgical T staging (n = 26), overall ICC was 0.844 for PET/CT (reader 1 0.853, reader 2 0.835) and 0.874 for PET+MR (reader 1 0.86, reader 2 0.888).
  • Against surgical N staging (n = 26), overall ICC was 0.551 for PET/CT (reader 1 0.595, reader 2 0.506) and 0.666 for PET+MR (reader 1 0.683, reader 2 0.649). The authors reported that PET+MR N stages agreed better with pathology than PET/CT N stages did.
  • T stage was correct in 17 of 26 patients (65%) for both readers with both PET/CT and PET+MR. N stage was correct in 16 (62%) with PET/CT and 17 (65%) with PET+MR, for both readers.
  • Both methods tended to overestimate lower T stages (T1 to T2) and underestimate higher T stages (T3 to T4), compared with pathology.
  • The authors reported diagnostic confidence as significantly higher for PET+MR than for PET/CT: mean score 1.66 versus 1.93, p = 0.003. The abstract gives p = 0.004. The Methods describe the scale as 1 = unsure and 3 = high confidence, while the abstract describes it as running from sure to unsure.
  • Image quality was rated diagnostic for all image series.
• The authors' conclusion: The authors concluded that their findings suggest PET+MR's diagnostic accuracy is comparable to PET/CT for local staging of malignant pleural mesothelioma, and that radiologists felt significantly more confident staging with PET+MR when dedicated sequences were used.
• Limitations the authors state:
  • PET+MR and PET/CT used different slice thicknesses, which might cause missed lesions and partial volume effects.
  • Histopathology was available as the reference standard for only 26 of the 34 patients.
  • Many patients had stage T3 disease (15 of 26), which may bias the findings.
  • Surgical pathology was influenced by preoperative imaging, so the reference standard was not truly independent.

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: Staging, Pleural Mesothelioma, Clinical Trial, Discovery, Histopathology.

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