Use of computed tomography and positron emission tomography/computed tomography for staging of local extent in patients with malignant pleural mesothelioma

Our plain-English summary of Use of computed tomography and positron emission tomography/computed tomography for staging of local extent in patients with malignant pleural mesothelioma, by T. Frauenfelder, P. Kestenholz, R. Hunziker, et al (Journal of Computer Assisted Tomography, 2015).

The study

• Authors: T. Frauenfelder, P. Kestenholz, R. Hunziker, T.D. Nguyen, M. Fries, P. Veit-Haibach, L. Husmann, R. Stahel, W. Weder, I. Opitz
• Journal: Journal of Computer Assisted Tomography
• Published: 2015;39(2):160-5
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: The objective of this study was to determine the diagnostic value of computed tomography (CT) and positron emission tomography (PET)/CT for staging of malignant pleural mesothelioma (MPM) in patients undergoing induction chemotherapy.

Methods: Sixty-two patients (median age, 61 years; female: n = 9) with proven MPM underwent CT after induction chemotherapy. Of these, 28 underwent additional PET/CT. Extrapleural pneumonectomy was performed for pathological TNM staging. Clinical TNM stage was assessed by 3 independent readers. Relative and absolute underestimation and overestimation were compared with pathological tumor stage. Sensitivity, specificity, and accuracy for differentiation between stages T2 and T3 were assessed. Interobserver agreement between the readers was analyzed (κ).

Results: Positron emission tomography/CT and CT underestimated T stage in up to 30% of the cases. Positron emission tomography/CT had a higher accuracy for tumor extent compared with CT (PET/CT: 0.92; CT: 0.84). The accuracy for nodal staging was higher for CT than for PET/CT (PET/CT: 0.78; CT: 0.87). Concerning International Mesothelioma Interest Group classification, PET/CT improved the accuracy of preoperative staging compared with CT (PET/CT: 0.91; CT: 0.82). Interobserver agreement was moderate for CT (0.48-0.62) and good for PET/CT (0.64-0.83) for T staging. For nodal staging, interobserver agreement was fair to moderate for CT and good for PET/CT (CT: 0.37-0.51; PET/CT: 0.73-0.76).

Conclusions: Positron emission tomography/CT is more accurate and has a lower interobserver variability for clinical intrathoracic staging of MPM compared with CT. Nevertheless PET/CT underestimated tumor stage in a substantial number of cases, showing the need for a more accurate imaging technology or approach.

In plain English

This retrospective study looked at 62 patients with malignant pleural mesothelioma who had induction chemotherapy and then extrapleural pneumonectomy over a 12-year period. It did not examine asbestos exposure. It compared two imaging methods for staging the cancer before surgery, CT and PET/CT, using surgical pathology as the reference. Three readers, blinded to clinical information, staged all 62 patients from CT. Three readers staged the 26 patients who also had PET/CT. Both methods often understaged the tumor. CT readers underestimated T stage in 22% to 27% of the 62 patients, and PET/CT readers in 4% to 19% of the 26. For stage T4 disease, accuracy was 84% for one CT reader and 92% for one PET/CT reader. For lymph-node stages N2 and N3, accuracy was 87% for one CT reader and 78% for one PET/CT reader. Agreement between readers was generally higher for PET/CT. The authors concluded that PET/CT underestimated stage in a substantial number of cases and that invasive staging such as mediastinoscopy is still necessary. They also concluded that no reliable imaging technique exists yet, although PET/CT is favored. They noted that the PET/CT group was small.

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 diagnostic accuracy study comparing CT and PET/CT staging with pathological staging after surgery
• Who was studied: 62 patients with malignant pleural mesothelioma (median age 61, range 38 to 72; 9 female, 53 male) who had induction chemotherapy followed by extrapleural pneumonectomy over a 12-year period. Histology was epithelioid in 39, sarcomatoid in 1 and biphasic in 22. 26 of them also had PET/CT. The authors were based at the University Hospital of Zurich, Switzerland.
• Exposure: No asbestos exposure was assessed. The study evaluated imaging: contrast-enhanced CT in all 62 patients and PET/CT in 26 patients, performed after induction chemotherapy (cisplatin with gemcitabine in 9 patients, cisplatin with pemetrexed in 53) and before surgery.
• Main results:
  • CT, all 62 patients: tumor extent (T stage) was underestimated by 14 patients (22%) for readers CT-R1 and CT-R3 and by 17 patients (27%) for reader CT-R2.
  • PET/CT, 26 patients: T stage was underestimated in 4 (15%), 5 (19%) and 1 (4%) patients for the three readers. The authors reported that underestimation was less frequent than with CT.
  • Stage T4 disease. For CT reader CT-R1, sensitivity was 40%, specificity 95%, positive predictive value 66%, negative predictive value 87% and accuracy 84%.
  • Stage T4 disease. For PET/CT reader PET/CT-R2, sensitivity was 80%, specificity 95%, positive predictive value 80%, negative predictive value 95% and accuracy 92%. The authors described this as higher than CT.
  • Lymph-node stages N2 and N3. For CT reader CT-R1, sensitivity was 70%, specificity 97%, positive predictive value 85%, negative predictive value 88% and accuracy 87%.
  • Lymph-node stages N2 and N3. For PET/CT reader PET/CT-R2, sensitivity was 80%, specificity 78%, positive predictive value 57%, negative predictive value 91% and accuracy 78%. The authors described this as lower than CT. N stage was correctly assessed in 54% of cases.
  • IMIG stage IV. Accuracy was 82% for CT reader CT-R1 (sensitivity 50%, specificity 89%) and 91% for PET/CT reader PET/CT-R2 (sensitivity 66%, specificity 95%).
  • Among the 26 patients who had both scans, N stage was more often understaged on PET/CT than on CT. In particular, pathologic stage N2 was staged as N0 on PET/CT.
  • Agreement between CT readers (kappa) was 0.73, 0.52 and 0.48 for T staging, described as moderate to good, and 0.43, 0.51 and 0.37 for N staging, described as fair to moderate.
  • Agreement between PET/CT readers (kappa) was described as good for both T staging (0.71, 0.63, 0.64) and N staging (0.75, 0.76, 0.73).
• The authors' conclusion: The authors concluded that PET/CT underestimated tumor stage in a substantial number of cases, so invasive staging such as mediastinoscopy is still necessary. They concluded that neither method yet provides reliable imaging of local tumor extent, although PET/CT is favored, particularly because readers agreed with each other more often than with CT.
• Limitations the authors state:
  • The number of patients who had both PET/CT and CT was low.
  • Stage T3 disease made up a large share of the cohort (19 of 26 patients), which may bias the findings.
  • CT and PET/CT were read by partly different readers, because some readers lacked PET/CT expertise.
  • The pathology reference standard was not truly independent, because surgical samples are affected by the preoperative imaging.
  • Patients who had talc pleurodesis were included. Talc pleurodesis causes inflammation that might influence the accuracy of PET/CT staging.

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, Chemotherapy, Extrapleural Pneumonectomy (EPP), TNM Staging, Mesothelioma, Intrathoracic.

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