Staging is the term for the process of determining how far advanced a cancer is, and how far it is spread from the original site. The goal of mesothelioma staging is to determine what kinds of treatment options will be most helpful, and what a person's life expectancy will be. All systems use four stages to describe the progress of mesothelioma. Stage I is the earliest, and Stage IV is the most advanced. Pleural mesothelioma is the most common form of the disease, and the only one for which staging classifications has been developed.
Three mesothelioma staging systems are in use, each focusing on a particular aspect of the disease.
The oldest, the Butchart system, stages mesotheliomas according to the size of the original tumor and how much it has invaded other organs. Although it is widely used, it has less predictive value for planning treatment.
The TNM (Tumor/Node/Metastasis) system developed by the International Mesothelioma Interest Group and adopted by the American Joint Committee on Cancer (AJCC) takes into account the size of the original tumor, the degree of involvement of the lymph nodes, which are the means by which tumors spread around the body, and how far the tumor has spread. It is similar to staging systems used for most other cancers, and it has been adopted by most US cancer centers. Its stages are shown in the table below.
|TNM Mesothelioma Staging System|
|STAGE||PROGRESS OF TUMOR|
|I||Mesothelioma involves the linings of the lung, diaphragm, or pericardium on same side. No lymph node involvement|
|II||Mesothelioma has spread to lymph nodes on same side as involved lining tissue. It may also have spread to the lung, diaphragm, and pericardium.|
|III||Mesothelioma now found in chest wall, muscle, ribs, heart, esophagus, or other organs in the chest on the same side as the primary tumor.|
|IV||Mesothelioma has now metastasized to the opposite lymph nodes, and/or the opposite lung. Organs in the neck or the abdominal cavity may also be involved.|
The Brigham system, the most recently developed mesothelioma staging system, evaluates mesothelioma from the perspective of surgical removal (resectability) and lymph node involvement. Its stages are shown below.
|Brigham Mesothelioma Staging System|
|STAGE||PROGRESS OF TUMOR|
|I||The tumor can be surgically removed, and there is no lymph node involvement|
|II||The tumor can be surgically removed, but the mesothelioma has now involved the lymph nodes.|
|III||The tumor cannot be surgically removed. It extends into the chest wall, the heart, or through the diaphragm into the peritoneum. Lymph node involvement may or may not be present.|
|IV||Mesothelioma has now metastasized to other, distant organs|
In all mesothelioma staging systems patients with Stages I and II mesotheliomas will likely be candidates for surgery, followed by multiple-drug chemotherapy. Patents whose stage 3 and stage 4 patients are generally offered chemotherapy in combination therapies. Staging the mesothelioma is essential for making sound choices about treatment options and for determining the prognosis for mesothelioma patients.