In September of last year, the International Association for the Study of Lung Cancer (IASLC) released an update to the TNM staging system for pleural mesothelioma. This update is the ninth edition and reflects a more comprehensive understanding of the rare, asbestos-related disease. The improvements reflect a larger, more diverse patient database that includes over 3,500 cases from six continents.
Changes in Mesothelioma Tumor (T) Evaluation Standards
The TNM staging system is a standard international method used to classify all types of cancer, including mesothelioma. It evaluates the extent of cancer using Tumor size and invasion (T), Node involvement in nearby lymph nodes (N), and Metastasis or spread to distant parts of the body (M). The system helps physicians evaluate the severity of the patient’s condition, create a treatment plan, and track outcomes. TNM staging standards are revised as more is learned about the specific disease.
The ninth edition of the TNM staging classification of pleural mesothelioma reflects years of research into the rare form of cancer. Though several changes were made, the most significant involves how doctors measure and classify mesothelioma tumor size. In the past, staging relied mainly on whether the tumor had spread to nearby structures within the body, but the 9th edition adds a standardized measurement system using CT scans. By measuring the thickest part of the tumor in three equal sections, doctors can provide more objective, measurable criteria that will be the same across different hospitals, and even in different countries.
The new system also recognizes mesothelioma tumor involvement in the spaces between lung lobes, indicating that when a side-view CT scan reveals tumors in these areas thicker than 5 millimeters, they are automatically classified as T2 tumors, indicating more advanced disease.
The Stage Groups in Pleural Mesothelioma Remain the Same
There are several aspects of the staging criteria for pleural mesothelioma that are remaining the same, though they have been simplified and reorganized. The separate Stage IA and IB categories that were previously used have now merged into a single Stage I, which only includes the earliest tumors. Stage II now includes slightly more advanced tumors, and the boundaries between Stage IIIA and other stages have shifted based on tumor characteristics.
Beyond those changes, the lymph node classification from the 8th edition, which recognizes that mesothelioma spreads to lymph nodes differently than lung cancer, has not changed. The metastasis component, which notes the differences between patients without distant spread and those with cancer that has spread to other organs, also remains the same, as does the way that pathological staging is done, as accurate thickness measurements of tumors are impossible after surgeons remove the tumors in pieces.
These revisions, which reflect increased understanding of this rare and deadly disease, create a more accurate, measurable staging system that better predicts mesothelioma patient outcomes and helps guide treatment decisions. If you or someone you love has been diagnosed with mesothelioma and you need help, contact the Patient Advocates at Mesothelioma.net today at 1-800-692-8608.
