A proposed new international TNM staging system for malignant pleural mesothelioma from the International Mesothelioma Interest Group

Our plain-English summary of A proposed new international TNM staging system for malignant pleural mesothelioma from the International Mesothelioma Interest Group, by V.W. Rusch (Lung Cancer, 1996).

The study

• Author: V.W. Rusch
• Journal: Lung Cancer
• Published: 1996;14(1):1-12
• Cited by: 109 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Study Objective: investigation of the behavior and treatment of diffuse malignant pleural mesothelioma (MPM) is hindered by the lack of an accurate universally accepted staging system. To address this problem, the International Mesothelioma Interest Group (IMIG) has developed a new TNM based staging system.

Methods: the staging system was developed at a consensus meeting of IMIG members involved in clinical research in MPM, including the originators of previously proposed staging systems. The new staging system is based on the analysis of emerging information about the impact of T and N status on survival.

Results: in contrast to five previous staging systems, the T descriptors designated as T1, T2, T3 and T4, provide precise anatomic definitions of the local extent of the primary tumour. The N descriptors, designated as N0, N1, N2 and N3, are virtually identical to those used in the International Lung Cancer Staging System. The stage groupings recognize new data about the better prognosis of T1 and N0 tumours and classify those tumours into stages I and II. The adverse impact of nodal metastases on survival noted in some recent surgical series warrants placing node positive tumours in stage III. Locally advanced unresectable (T4) tumours and extrathoracic disease (N3 or M1) are classified as stage IV.

Conclusion: this proposed staging system reconciles and updates several earlier systems, and can provide the framework for analyzing the results of prospective clinical trials aimed at improving the currently dismal prognosis of MPM.

In plain English

This meeting report, written on behalf of the International Mesothelioma Interest Group (IMIG), proposed a new staging system for malignant pleural mesothelioma. It did not study patients or asbestos exposure directly. IMIG members who had led large case series or trials met in June 1994, presented survival data by tumour extent and lymph node spread, and agreed the system by consensus. The system defines tumour categories T1 (T1a and T1b) through T4. T3 is described as potentially removable by surgery and T4 as technically unresectable. Lymph node categories were stated to be identical to those of lung cancer staging. Stage I covers T1a and T1b tumours and stage II covers T2 tumours, both without lymph node or distant spread. Stage III covers T3 tumours and N1 or N2 node spread, without distant spread. Stage IV covers any T4 tumour, N3 node spread or distant spread. Some distinctions were stated to rest on limited survival data. The author stated it was not meant to be definitive or to justify treatments such as surgery, but as an agreed basis for future studies.

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: Meeting report presenting a consensus-based staging proposal (not an original study of patients)
• Who was studied: Members of the International Mesothelioma Interest Group who were primary authors of large retrospective series or principal investigators in clinical trials in malignant pleural mesothelioma. The consensus meeting was held in June 1994 during the 7th World Conference of the International Association for the Study of Lung Cancer. The appendix lists 13 major contributors.
• Main results:
  • Stages I and II include only node-negative tumours. Stage I is subdivided into Ia and Ib based on T1a versus T1b, and stage II includes T2N0 tumours. In Table 6 these stages are also M0 (no distant metastasis).
  • Stage III includes any T3, any N1 or any N2 tumours without distant metastasis (M0). Stage IV includes any T4, N3 or M1 tumours.
  • T3 is defined as locally advanced but potentially resectable tumour. T4 is defined as locally advanced, technically unresectable tumour.
  • The lymph node (N) descriptors are stated to be identical to those of the International Lung Cancer Staging System.
  • N1 and N2 disease were both grouped in stage III because the available survival data could not separate these node groups.
  • The author stated that clinical trials should also stratify patients by tumour histology for survival analysis.
• The authors' conclusion: The author concluded that the proposed system is not meant to be definitive or to justify particular treatments such as surgical resection. It is meant to form an internationally agreed basis for future prospective studies that would refine the system and assess new treatments.
• Limitations the authors state:
  • Fewer survival data support the distinction between T1b and T2 tumours than between T1a and T1b tumours.
  • Where to place T1b and T2 N0 tumours was described as a difficult, unresolved issue needing more data.
  • T1a and T1b are difficult to tell apart on imaging, and the system presumes that most early tumours are evaluated surgically and pathologically.
  • No TNM system fully captures the pathological and biological factors that affect survival.

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, Mesothelioma, Staging, IMIG, Lung Cancer, Stage Grouping, Prognosis.

Related studies

• Recommendations for uniform definitions of surgical techniques for malignant pleural mesothelioma: a consensus report of the international association for the study of lung cancer international staging committee and the international mesothelioma interest group — D. Rice, V. Rusch, et al. (2011)
• Evaluation of the clinical TNM staging system for malignant pleural mesothelioma: an assessment in 88 patients — L. Tammilehto, L. Kivisaari, et al. (1995)
• Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma. Complementary statement from the International Mesothelioma Interest Group, also endorsed by the International Academy of Cytology and the Papanicolaou Society of Cytopathology — A. Hjerpe, V. Ascoli, et al. (2015)
• Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma: Complementary statement from the international mesothelioma interest group, also endorsed by the international academy of cytology and the papanicolaou society of cytopathology. A proposal to be applauded and promoted but which requires updating — M. Sheaff (2020)
• Management of malignant pleural mesothelioma - part 1: epidemiology, diagnosis, and staging : Consensus of the Austrian Mesothelioma Interest Group (AMIG) — C. Geltner, P. Errhalt, et al. (2016)
• Peritoneal mesothelioma proposal for a staging system — G. Sebbag, P.H. Sugarbaker (2001)

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