Staging a disease is the process of detailing a diagnosis to the point that the progress of the disease is pinpointed. For lethal afflictions such as asbestos cancer, the staging process is important because it will play a major role in dictating treatment procedures. It is crucial that physicians understand staging systems and use them for communications purposes, so that one doctor knows what another has observed, or what tests have shown, or what a patient may have revealed. It's a delicate process; a missed cell count on a pathological exam could lead to a misdiagnosis and the spread of the cancer, leading in turn to the wrong treatment choices and a diminished chance of survival for the patient.
Mesothelioma Stages - TNM System
Because malignant mesothelioma is a rare disease and because two thirds or more of all cases have arisen in the chest, pleural mesothelioma is the only form of the disease for which a formal staging system has been devised. The most common of the three staging methodologies used today in diagnosing mesothelioma is the TNM system, an acronym for Tumor, Nodes, and Metastases.
Generally these three categories designate degrees of advancement, but there are also stages for each of these terms. The tumor – or in the case of mesothelioma, tumors – may be ranked at stage 2, diffuse but still localized. There may be the beginnings of lymph node infiltration of malignancy, also still localized – stage 1. And there may be no evidence of impact on organs or tissues removed from the mesothelium where the tumors are located, so a 0 stage for metastasis. That would be a T2N1M0 stage for pleural mesothelioma.
In general however the TNM staging system divides mesothelioma into four stages, as with most cancer staging systems. In looking at these steps it is worth noting that mesothelioma cancer always evolves on one side of the body or the other; usually on the right side. These are the general parameters for mesothelioma TNM staging:
Stage I Mesothelioma is present in the right or left pleural cavity and may have metastasized to the lung, pericardium (sac around the heart), or diaphragm on the same side. Lymph nodes are not involved.
Stage II Mesothelioma has reached from one side of the pleural cavity to a lymph node near the lung area on the same side. The cancer has also metastasized to the diaphragm, pericardium, or lung on the same side.
Stage III Mesothelioma has penetrated the chest lining, heart, esophagus, muscle, ribs, and vital organs in the chest cavity on the same side. Lymph nodes may or may not be involved.
Stage IV Mesothelioma has metastasized to the pleural area and lymph nodes on the opposite side of the tumor, or has reached the chest cavity or lung on both sides, or has spread to vital organs in the abdomen.
When this system was adapted for mesothelioma in 1995 surgery was not nearly as prevalent in the treatment of mesothelioma. For that reason a more recent iteration of a mesothelioma staging methodology centers on surgical viability. Fifteen years after the TNM system was devised for mesothelioma, surgical techniques, new chemotherapy drugs and techniques, and targeted radiotherapy have created some effective treatment options that some surgeons feel should be subject to an updated staging system.
Brigham Staging System for Mesothelioma Cancer
Brigham Staging System is the most recent staging system for mesothelioma and looks at variables such as lymph node status and tumor resectability (ability to surgically remove a tumor). The Brigham staging system consists of four stages:
Stage I Mesothelioma is still resectable and localized with lymph nodes unaffected
Stage II Mesothelioma is still resectable. Lymph nodes have been affected.
Stage III Mesothelioma is not resectable and has penetrated the chest wall, heart, abdominal cavity, or diaphragm. Lymph nodes may or may not be affected.
Stage IV Mesothelioma has completely metastasized.
Butchart Staging System for Mesothelioma
Butchart System is the oldest mesothelioma staging system, it is based on the size of the tumor mass and divides the cancer into four different stages:
Stage I Mesothelioma has affected the right or left side of the pleura (chest) cavity, and may also be seen in the diaphragm.
Stage II Mesothelioma has penetrated the chest lining into the heart, pleura, or esophagus on both sides. Lymph nodes may be affected.
Stage III Mesothelioma has reached the peritoneum (abdominal cavity). Lymph nodes past the chest may be affected.
Stage IV Mesothelioma has entered the bloodstream and reached other organs
- Treatment of Mesothelioma Based on Extent of Cancer, American Cancer Society, http://www.cancer.org/docroot/cri/content/cri_2_4_4x_treatment_options_by_stage_29.asp
- Proposed New International TNM Staging System for Malignant Pleural Mesothelioma, Chest, June 1995, http://chestjournal.chestpubs.org/content/108/4/1122.full.pdf+html
- Extrapleural Pneumonectomy, Cardiothoracic Surgery Network, http://www.ctsnet.org/sections/clinicalresources/thoracic/expert_tech-7.html