Evaluation of the clinical TNM staging system for malignant pleural mesothelioma: an assessment in 88 patients

Our plain-English summary of Evaluation of the clinical TNM staging system for malignant pleural mesothelioma: an assessment in 88 patients, by L. Tammilehto, L. Kivisaari, U.S. Salminen, et al (Lung Cancer, 1995).

The study

• Authors: L. Tammilehto, L. Kivisaari, U.S. Salminen, P. Maasilta, K. Mattson
• Journal: Lung Cancer
• Published: 1995;12(1-2):25-34
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

There is no universally-recognised method for staging malignant mesothelioma, although the use of computed tomograph (CT) scanning has improved the staging of non-invasive disease. The International Union against Cancer has recently proposed using the Tumour Node Metastases (TNM) staging system for mesothelioma, but in clinical practice it is difficult to assess tumour and nodal involvement due to the unique plate-like growth pattern of this tumour. In order to evaluate TNM staging we analysed pre-operative CT scans from 88 patients with histologically-confirmed malignant pleural mesothelioma, all from the same institution. The median age of the patients was 56 years (range 38-79). There were 70 men and 18 women, and 33 had tumours with epithelial histology. The median survival time was 10 months (range 0.2-110), from the date of histological confirmation of mesothelioma. The same radiologist analysed all the CT scans according to the TNM staging system. Actuarial survival curves were constructed by the Kaplan-Meier method. Survival curves for the different TNM categories were compared using the log-rank test. Node evaluation could not be completed in eight cases because the tumour had encompassed the hilum and mediastinum. In multivariate analysis, significant differences in prognosis correlated with the different T categories (P < 0.01), and the different TNM stages (P < 0.05), but not the N categories or the M categories. Larger studies are needed to assess the importance of TNM staging in the selection of treatment and as a prognostic factor for malignant mesothelioma.

In plain English

This Finnish study tested whether the TNM staging system (tumour, lymph nodes, distant metastases) could be applied to malignant pleural mesothelioma using pre-treatment CT scans. It included 88 patients diagnosed between 1982 and 1991 at Helsinki University Central Hospital: 70 men and 18 women, median age 56. One radiologist staged every scan. The tumour (T) category could be assessed in every case. Lymph node status could not be assessed in eight cases, where the tumour surrounded the hilum and mediastinum. Distant metastases could not be assessed in five. Median survival, measured from first histological confirmation of mesothelioma, was 10 months (range 0.2 to 110). Survival differed significantly by T category (P = 0.0043) and by overall TNM stage (P = 0.0132), but not by node status or metastases. Node and stage groups were very unbalanced, and only two patients had Stage II disease. The authors concluded that T status from CT was an accurate guide to prognosis. They found that N status could not be determined accurately enough for true TNM staging, and they called for larger studies. Occupational histories were recorded, but no asbestos exposure findings were reported.

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 analysis of pre-treatment CT scans staged by one radiologist under the TNM system, with survival compared across TNM categories (Kaplan-Meier curves, log-rank test, Cox proportional hazards model)
• Who was studied: 88 patients with histologically confirmed malignant pleural mesothelioma, drawn from 116 patients diagnosed with malignant mesothelioma by the Mesothelioma Pathology Panel at Helsinki University Central Hospital, Finland, between 1982 and 1991. Excluded were 6 patients with peritoneal tumours and 12 pleural patients without adequate pre-treatment CT scans. The 88 were 70 men and 18 women, median age 56 years (range 38-79).
• Exposure: Not analysed. The article says an occupational history was documented for each patient but reports no asbestos exposure data. The study examined CT-based TNM staging, not exposure.
• Main results:
  • Among all 88 patients, median survival measured from the date of first histological confirmation of mesothelioma was 10 months (range 0.2 to 110). Eight patients were alive at the time of analysis.
  • The T category could be assessed in every case. Lymph node (N) evaluation could not be completed in eight cases (9%) because the tumour had encompassed the hilum and mediastinum.
  • Distant metastases could not be evaluated in five cases (6%). The lung was collapsed in two, and the lung window setting was not used in three.
  • Metastases were detected in 14% (12/83) of the CT scans.
  • Node groups were very unbalanced: N0 58 patients, N1 5, N2 15, N3 2.
  • T categories were T1 19 patients, T2 16, T3 41, T4 12. Survival differed significantly by T category (P = 0.0043) and by TNM stage (P = 0.0132). Histological subtype (P = 0.0099) and performance status (P = 0.0001) also correlated significantly with survival.
  • Neither node status nor the presence or absence of metastases was significant for prognosis.
  • When nodes were split into N0 (median survival 11.5 months) and all others (median survival 10 months), there was still no significant correlation with survival (P = 0.1667).
• The authors' conclusion: The authors concluded that T status determined clinically from CT was an accurate guide to prognosis, but N status could not be determined accurately enough for true TNM staging to be performed. They called for larger studies to assess clinical TNM staging, especially N status evaluation, for selecting treatment and as a prognostic factor in malignant pleural mesothelioma.
• Limitations the authors state:
  • Node status could not be evaluated from CT in some patients, which the authors describe as a shortcoming of radiographic staging in this disease.
  • The stage groups were unbalanced, with only two patients in Stage II.
  • Technical developments in CT scanning after this study might affect the ability to correlate nodal status with outcome.

Topics

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

Medical terms in this study, explained in our Lexicon: TNM Staging, Pleural Mesothelioma, Staging, Malignant Mesothelioma, Mesothelioma, CT Scan, Histology, Median Survival.

Related studies

• A proposed new international TNM staging system for malignant pleural mesothelioma from the International Mesothelioma Interest Group — V.W. Rusch (1996)
• Peritoneal mesothelioma proposal for a staging system — G. Sebbag, P.H. Sugarbaker (2001)
• Challenging a dogma; AJCC 8th staging system is not sufficient to predict outcomes of patients with malignant pleural mesothelioma — O. Abdel-Rahman (2017)
• The revised staging system for malignant pleural mesothelioma based on surveillance, epidemiology, and end results database — S. Wang, K. Ma, et al. (2017)
• Robust data: the essential foundation of a revised staging system for pleural mesothelioma — H.L. Kindler (2012)
• Staging of patients after extrapleural pneumonectomy for malignant pleural mesothelioma--institutional review and current update — C. Cao, S.K. Krog Andvik, et al. (2011)

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