The International Mesothelioma Interest Group (IMIG) staging system has been widely used, however, widespread concerns exist about the validity of the current malignant pleural mesothelioma (MPM) staging system. Concerns include that the system is derived from analysis of small, retrospective surgical series; it can be difficult to apply to clinical staging; and uses descriptors for lymph node involvement, which may not be relevant to MPM. Therefore, in collaboration with IMIG, the International Association for the Study of Lung Cancer (IASLC) has decided to update the staging system for MPM by developing a large international database.
A study, published in the November 2012 issue of the IASLC'S Journal of Thoracic Oncology, reports the current staging system by and large appropriately distinguishes among T and N categories and overall stages but also highlights areas for potential revision.
The study looked at 3,101 patients from 15 centers in four continents. The current data still represents mainly surgically treated patients. The authors report that current T descriptors are qualitative and most applicable to pathological staging. Possibly in the future, volumetric tumor measurement could enhance the current T descriptors.
In addition, the data demonstrate a difference in survival for node-negative versus node-positive patients. The difference between N1 and N2 disease is less clear, suggesting that additional study of the extent of lymph node involvement might yield improvements in the N-classification factor.
And finally the authors suggest that staging groups, especially for stages I and II disease, need to be reassessed. In the future, they say, "the addition of a larger group of patients with more advanced disease, staged clinically and managed nonsurgically may help determine whether stages III and IV should be classified into a and b subcategories."
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