Chest
Volume 108, Issue 4, October 1995, Pages 1122-1128
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Special Report: Articles
A Proposed New International TNM Staging System for Malignant Pleural Mesothelioma

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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 tumor. The N descriptors, designated as NO, 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 TI and NO tumors and classify those tumors into stages I and II. The adverse impact of nodal metastases on survival noted in some recent surgical series warrants placing node-positive tumors in stage III. Locally advanced unresectable (T4) tumors and extrathoracic disease (N3 or Ml) 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.

Section snippets

Materials and Methods

The IMIG members listed in Appendix I who have been primary authors of large retrospective series or principal investigators in clinical trials in MPM presented their data with respect to the influence of T and N status and of other potential prognostic factors on overall survival. These data were used to create a TNM-based system that potentially can be applied to the radiographic, surgical, and pathologic staging of MPM. The precise TNM descriptors were developed by consensus during the

Results

The proposed new International Staging System for MPM is shown in Table 6. It includes precise TNM descriptors that are grouped into a stage I through IV classification. Though potentially applicable to radiographic staging by CT scan, these TNM descriptors are primarily based on surgical and pathologic findings.

T1 is divided into la and 1b. T1a describes a very early tumor that involves only the ipsilateral parietal pleura with or without tumor on the diaphragmatic or mediastinal pleura. The

Discussion

Until 30 years ago, MPM was thought to be a rare and idiopathic tumor. The link between asbestos exposure and the subsequent development of MPM was first established in 1960 by Wagner et al.12 Because of the histologic similarities between the epithelial form of MPM and adenocarcinoma, accurate pathologic diagnosis of MPM was initially challenging. It only became routine with the advent of electron microscopy and the increasing use of immunohis-tochemistry.13,14 The importance of CT scanning

ACKNOWLEDGMENT

The authors wish to acknowledge Melody Owens for her expert assistance in the preparation of this manuscript.

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    Prepared by Valerie W. Rusch, MD, Attending Surgeon, Thoracic Service, Department of Surgery, and Member, Memorial Sloan-Kettering Cancer Center, New York.

    This work was funded in part by educational grants from the International Association for the Study of Lung Cancer and the Oncology Division of the Bristol-Myers Corporation.

    revision accepted June 7

    Members of the International Mesothelioma Interest Groups are listed in the Appendices at the end of this article.

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