The term “staging” is used to define the extent to which a cancer has spread in the patient’s body. Staging of mesothelioma is determined through the use of physical exams, biopsies, and medical imaging tests such as MRI and PET scans. Staging is an essential tool for determining what the most effective mesothelioma treatments will be for the patient. Staging also strongly affects a patient’s prognosis or outlook.
There are several clinical systems existing today for staging pleural mesothelioma, the most common form of the disease. They are the TNM Staging System, the Butchart Staging System, and the Brigham and Women’s Staging System.
TNM Staging System
The TNM staging system is the most widely accepted and it is endorsed by both the International Mesothelioma Interest Group and the American Joint Commission on Cancer. The system’s stages represent the main aspects of the diagnosis. According to the National Cancer Institute, these are:
- T – The degree to which the primary tumor has spread
- L – Whether the cancer has infiltrated nearby lymph nodes
- M – The extent of metastasis or spread of cancer to other organs.
The numbers 0 through 4 are added to each letter to identify the stage of the tumor and its spread. A more advanced cancer has a higher number.
- TX: It is not possible to evaluate main tumor
- T0: No evidence of main tumor found
- T1: Mesothelioma is limited to one side of the chest’s pleural lining and possibly the diaphragm, mediastinum (the space between the lungs), or the pleura covering the lung on that side.
- T2: The cancer involves the pleural lining of the chest and the pleura of the diaphragm, mediastinum, and lung, though it remains located on one side of the chest. It has also spread to the diaphragm, the lung, or both.
- T3: The cancer has grown but may still be surgically removed. It now also extends into at least one of these areas: the endothoracic fascia, the fat of the mediastinum, deep into the chest wall, or the heart’s outer layer.
- T4: Surgery can no longer remove the mesothelioma. In addition to encompassing the pleural lining of chest and the pleura of the diaphragm, mediastinum, and lung on one side, it has also grown into one or more of these areas: the chest wall and its muscles and ribs, peritoneum, esophagus, trachea, thymus, blood vessels, spine, heart, and pleura on the opposite side of the chest.
Lymph Nodes (N)
- NX: Not possible to assess nearby lymph nodes.
- N0: Mesothelioma hasn’t spread to nearby lymph nodes.
- N1: Mesothelioma now involves the lymph nodes in and/or around the lung on the side where the main tumor is located.
- N2: The cancer has spread to other lymph nodes next to the main tumor, including the subcarinal, mediastinal, and internal mammary nodes.
- N3: Mesothelioma now involves the supraclavicular lymph nodes and/or the hilar or mediastinal nodes on the side opposite the main tumor.
- MX: Not possible to assess metastasis
- M0: Cancer has not metastasized or spread to other organs or parts
- M1: The cancer has metastasized or spread to distant sites.
A process called “stage grouping” takes place after a determination of a patient’s T, N, and M categories. The TNM information is combined in order to assign the malignant mesothelioma an overall stage of I, II, III, or IV. Stage IV is the most advanced stage. A better patient prognosis is associated with lower stage numbers.
Butchart Staging System
The Butchart system is the oldest of the three staging systems used to describe malignant mesothelioma. It was devised by Dr. Eric G. Butchart in the 1970s and is useful for identifying a patient’s prognosis and choosing therapeutic options. The system is based on the size and spread of the primary pleural cancer and divided into four stages:
- Stage 1: The cancer is located in one side of the pleural membrane and occasionally the pericardium, diaphragm, or lung on that side. It has not metastized to nearby lymph nodes or beyond.
- Stage 2: The cancer has spread to the chest and/or the esophagus, both sides of the pleura, or the heart. Cancerous cells may also be present in the lymph nodes.
- Stage 3: The cancer has spread to the peritoneum via the diaphragm. The cancer may also be found in the lymph nodes located outside of the chest cavity.
- Stage 4: The cancer has spread extensively to other organs in the body such as the liver, brain, or bone.
The Brigham Staging System
This staging system for malignant mesothelioma was proposed by Dr. David Sugarbaker of Boston’s Brigham and Women’s Hospital and colleagues in 1993 and revised in 1998. The basis for the system is whether the mesothelioma is removable by surgery and whether the lymph nodes are affected. There are four stages:
- Stage 1: There are no lymph nodes containing cancer cells and surgery can be used to remove the malignant mesothelioma.
- Stage 2: The lymph nodes are affected but the mesothelioma can still be removed with surgery.
- Stage 3: The malignancy has spread into the chest wall, heart, or through the diaphragm into the peritoneum and it cannot be surgically removed. There lymph nodes may or may be affected.
- Stage 4: Mesothelioma has metastasized and spread to other organs such as the liver, brain, or bone.
The Brigham system of staging allows doctors to determine how far the cancer has advanced before providing a prognosis to the patient and determining the best treatment.
More is known regarding the risks surrounding pleural mesothelioma as opposed to the other types. This is due to the fact that it has been better studied as it is the predominant form of the illness. It has been found that the younger the patient and the greater their general health, the more likely they are to have a positive prognosis.
Of the three different forms of mesothelioma, epithelial mesothelioma results in the more positive prognosis. Biphasic mesothelioma is second in terms of seriousness, and fibrosarcomatous mesothelioma has the least favorable results.
- Doherty, Gerard M. (2010). Current Diagnosis and Treatment Surgery. 13th ed.
- Vanderbilt University Department of Thoracic Surgery
- University of Texas, M.D. Anderson Cancer Center: Staging of Malignant Pleural Mesothelioma
- National Cancer Institute
- The Oncologist