Mesothelioma Staging
Staging is a method of evaluating the progress of cancer in a patient. Using this information, doctors will establish a patient’s treatment plan and will try to define a patient’s prognosis. Staging for mesothelioma looks at the extent of the cancer’s development and its possible spread to other parts of the body. Since pleural mesothelioma occurs most frequently and has been studied the most, it is the only mesothelioma for which a staging classification exists.
Several medical approaches are utilized to determine the patient’s stage of mesothelioma, including x-rays, CT scans, and MRI scans. These imaging technologies provide insight into the advancement, extent, and spread of the cancer. However, mesothelioma’s nature as a diffuse disorder means these technologies are often limited in their ability to fully identify the scope of the cancer.
There are three recognized clinical staging systems for evaluating the spread and extent of pleural mesothelioma:
The Butchart System was the original staging method for mesothelioma, but the International Mesothelioma Interest Group’s (IMIG) TNM system has supplanted it among major cancer centers as a more accurate method for evaluating mesothelioma. The Brigham System is one of the latest methods for the staging of mesothelioma and is comparable to IMIG’s system.
TNM Staging System
The International Mesothelioma Interest Group’s TNM system for mesothelioma staging has been adopted by the American Joint Committee on Cancer (AJCC). This system, like most other cancer staging systems, uses a TNM-based classification, where:
- T
- T stands for tumor and the classification refers to its size and how far it has spread to nearby organs.
- N
- N stands for lymph nodes and the classification refers to the cancer having spread to regional or distant lymph nodes.
- M
- M is for metastasis and the classification refers to the cancer have spread (“metastasized”) to other organs.
In TNM staging, information about the tumor, lymph nodes, and metastasis is combined in a process called stage grouping to assign a stage described by Roman numerals from I to IV. This system has, for the most part, supplanted the Butchart system as the primary mesothelioma-staging system, although one will find some doctors still using Butchart.
TNM Staging System for Mesothelioma
- Stage I
- Mesothelioma involves either the right or left pleura lining the chest. It has only spread to the outer lining of the lung in, at most, a few small spots. It has not yet spread to the lymph nodes.
- Stage II
- Mesothelioma involves either the right or left pleura lining the chest and has spread from the lining of the chest into:
- the outer lining of the lung; or
- the diaphragm or; or
- into the lung itself.
- Stage III
- Mesothelioma involves either the right or left pleura lining the chest and has spread into:
- the first layer of the chest wall; or
- the fatty part of the mediastinum; or
- a single place in the chest wall; or
- the outer covering layer of the heart; or
- lymph nodes anywhere in the same side of the chest
- Stage IV
- Mesothelioma involves either the right or left pleura lining the chest and has spread:
- into the chest wall, either muscle or ribs; or
- through the diaphragm; or
- into any organ contained in the mediastinum (esophagus, trachea, thymus, blood vessels); or
- into the spine; or
- across to the pleura on the other side of the chest; or
- through the heart lining or into the heart itself; or
- into the brachial plexus (nerves leading to the arm); or
- into lymph nodes outside that side of the chest; or
- spread to other organs through the bloodstream.
Butchart Staging System
The staging system historically used for mesothelioma is the Butchart system. This system is based on the extent of the primary tumor mass, and, like the other systems, divides mesothelioma into stages I through IV. Many doctors will still use this system, even though TNM has surpassed it in for accuracy.
- Stage I
- Mesothelioma is present within the right or left pleura, and may also involve the lung, pericardium, or diaphragm (the muscle separating the chest from the abdomen) on the same side.
- Stage II
- Mesothelioma invades the chest wall or involves the esophagus (food passage connecting the throat to the stomach), heart, or pleura on both sides. The lymph nodes in the chest may also be involved.
- Stage III
- Mesothelioma has penetrated through the diaphragm into the peritoneum (lining of the abdominal cavity). Lymph nodes beyond those in the chest may also be involved.
- Stage IV
- There is evidence of distant metastases spread through the bloodstream to other organs.
The Brigham System
The Brigham System is the latest system and stages mesothelioma according to resectability (the ability to surgically remove) and lymph node involvement.
- Stage I
- Surgically removable tumor and no lymph node spread.
- Stage II
- Surgically removable tumor with lymph node disease.
- Stage III
- Tumor not surgically removable because tumor extends into the chest wall, to the heart, or through the diaphragm into the peritoneum (abdominal lining). Lymph nodes outside the chest may or may not have disease in them.
- Stage IV
- The disease spread to other parts of the body.
Your doctors may utilize one or more of the above staging systems to evaluate the extent of the mesothelioma, and identify appropriate treatment options.