From the blog

Changes to Staging System for Mesothelioma

Published: July 5, 2024

Malignant pleural mesothelioma is a rare cancer associated with asbestos exposure. Two very important aspects of treating mesothelioma are classification and staging. They are important because they guide treatment and predict outcomes. One system to classify cancers is the TNM system which was created by the IASLC. It classifies cancers based on their size and spread. The IASLC Mesothelioma Staging Project is now aiming to improve the N descriptors for the ninth edition. A new article focuses on mesothelioma staging and suggested changes for N descriptors.

The TNM staging system is a universally accepted way for staging cancer, including mesothelioma. There are three components that help with the categorization of cancer: T (Tumor), N (Node), and M (Metastasis). Tumor deals with the size and extent of the primary tumor, Node deals with whether or not the cancer has spread to regional lymph nodes, and Metastasis deals with the presence of distant metastatic spread. Each component is given a number value to represent the severity of cancer, which then helps determine the overall stage of the cancer.

Accurate staging of pleural mesothelioma is a critical step in the treatment process. It helps to guide decisions and predict patient prognosis. The first stage is Stage I, where cancer is localized to the pleura on one side of the chest and has not spread to lymph nodes or distant sites. Then there is stage II, where the cancer has spread to the pleura on one side and nearby lymph nodes. There is also stage III, where cancer has spread to the pleura, nearby lymph nodes, and may involve parts of the chest wall or diaphragm. Finally, there is stage IV, where cancer has spread to distant organs and tissues.

The IASLC Mesothelioma Staging Project is looking to refine staging to enhance its accuracy and clinical utility. The study analyzed 3,598 cases of pleural mesothelioma diagnosed between the years 2013 and 2022, focusing on the N categories (lymph node involvement). The existing 8th edition N categories (N0, N1, N2) all performed adequately in the 9th edition dataset. Patients in the N0 group (no lymph node involvement) had a median overall survival advantage of 23.2 months when compared with N1 patients (lymph node involvement) who had a median overall survival of 18.5 months. When patients in the N0 group had radical resection surgery they had a 3-year overall survival of 48 percent, which was significantly better than the group with lymph node involvement. There was no significant difference in survival between patients with single versus multiple station nodal metastases. The number of nodal stations sampled at the time of resection did not affect overall survival. Based on the data, the study concluded that changes to the “N” categories were not necessary for the ninth edition of the pleural mesothelioma staging system.

Accurate staging is crucial in the diagnosis and treatment of mesothelioma. It is important because it helps to determine the most appropriate treatment approach, like surgery, chemotherapy, or radiation therapy. It also gives critical information about the likely course and outcome of the disease. Finally, it is important because it ensures patients are appropriately selected for clinical trials, which are crucial for developing new treatments.

The IASLC Mesothelioma Staging project looked to improve the N classification for the TNM system’s 9th edition. This emphasizes accurate staging for pleural mesothelioma. Data from the study shows that the current N categories are effective. This ensures that doctors can accurately stage and plan treatments. It is crucial to know what stage someone is when diagnosed with mesothelioma. Updates to staging promise better care and better outcomes for mesothelioma patients.


Andrea Billie et al., “The International Association for the Study of Lung Cancer Mesothelioma Staging Project: Proposals for the “N” Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Pleural Mesothelioma” Journal of Thoracic Oncology (May 9, 2024). [Link]
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