Stages of Mesothelioma

Staging is the process of finding out how far the cancer has spread and is used to determine the treatment of the tumor. Staging has only been established for pleural mesothelioma, the most common form of the disease. It is based on imaging studies such as X-rays, MRI scans, and CT scans. The treatment and outlook for patients with mesothelioma largely depends on the stage (extent of spread) of their cancer.

There are three major systems developed for staging mesothelioma: Brigham System, TNM System, and the Butchart System.

The Brigham System is the latest system and stages mesothelioma according to resectability (the ability to surgically remove) and lymph node involvement. Its four stages are:

• Stage I - The tumor is surgically removable, and there is no lymph node involvement.
• Stage II - The tumor is surgically removable, and there is lymph node involvement.
• Stage III - The tumor is not surgically removable because it 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 has spread to other parts of the body.

The TNM System is another staging system recently developed by the International Mesothelioma Interest Group and adopted by the American Joint Committee on Cancer (AJCC). The T stands for tumor (its size and how far it has spread to nearby organs), the N stands for the spread to lymph nodes, and the M stands for metastasis (spread to distant organs). This system considers variables of tumor in mass and spread, lymph node involvement, and metastasis. This system is beginning to be used by major cancer centers because it more accurately depicts the extent of the tumor. Its four stages are:

• 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, the diaphragm, or into the lung itself.
• Stage III - Mesothelioma is now in the chest wall, muscle, ribs, heart, esophagus, or other organs in the chest on the same side with or without spread to lymph nodes on the same side as the primary tumor.
• Stage IV - Mesothelioma has spread into the lymph nodes in the chest on the side opposite the primary tumor, or extends to the pleura or lung on the opposite side, or directly extends into organs in the abdominal cavity or neck. Any distant metastasis is included in this stage.

The Butchart System is the oldest system and is still the most commonly used. Its four stages are based on the extent of primary tumor mass.

• 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. It is not growing into the chest wall.
• 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 – Mesothelioma as spread through the bloodstream to other organs (metastases).

There are many factors that affect the prognosis and the treatment options available, such as:

• The stage of the cancer - Staging is based on the size of the tumor, whether the cancer has spread to the lymph nodes, and whether the cancer has spread to other parts of the body.
• The size of the tumor.
• Whether the tumor can be removed completely by surgery.
• The amount of fluid in the chest or abdomen.
• The patient's age and general health, including lung and heart health.
• The type of mesothelioma cancer cells and how they look under a microscope.
• Whether the cancer has just been diagnosed or is a reoccurrence.