STAGES OF MESOTHELIOMA

STAGING DEFINITION

Staging is a method of evaluating the severity of cancer in a patient. The doctor will evaluate the mesothelioma and the extent to which it has developed and spread to other parts of the body.  The stages of the cancer are represented on a scale of I to IV, with stage IV being the most progressed manifestation of the disease.  Since pleural mesothelioma occurs most frequently and has been widely studied, it is the only type of mesothelioma for which a staging classification exists.

The stage of mesothelioma in a patient is identified after a diagnosis has been given and the results of the imaging and pathology tests have been fully analyzed. The advancement, extent and spread of the cancer will then determine an individual patient’s present stage. MRIs may be used to visualize the extent of tissue infiltration and PET scans may be used to identify the existence of distant metastases. This is important information to discover, as the stage is used to best determine the treatment and prognosis for the patient.  In addition to biopsies, imaging tests including x-rays, CT scans, and MRI scans are used to fully assess the tumor.  The advancement, extent and spread of the cancer identifies the stage of the mesothelioma.  The stage is used to best determine the treatment and prognosis for the patient.

STAGING SYSTEMS

There are three recognized clinical staging systems for evaluating the spread and extent of pleural mesothelioma:

• TNM Staging - most commonly used system by major cancer centers as a more accurate method for evaluating mesothelioma.
• Butchart System - oldest staging technique which measures the size and proximity of the tumor.
• Brigham System - assesses whether the tumor can be surgically removed; the least used staging system.

TNM Staging System
The TNM staging system has recently been developed by the International Mesothelioma Interest Group and adopted by the American Joint Committee on Cancer (AJCC). TNM describes three key pieces of information related to the cancer. 

•  T stands for tumor indicating the size and extent to which it has spread to nearby organs.
•  N denotes how much the cancer has spread to lymph nodes.
•  M indicates whether the cancer has metastasized or spread to other organs.

The TNM information is then categorized, called stage grouping, and assigned a stage number from I to IV.

• 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 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 either:
                                   i.            the outer lining of the lung, or
                                  ii.            the diaphragm, or
                                 iii.            the lung
• Stage III: Mesothelioma involves either the right or left pleura lining the chest and has spread into either:
                                   i.            the first layer of the chest wall, or
                                  ii.            the fatty part of the mediastinum, or
                                 iii.            a single place in the chest wall, or
                                 iv.            the outer covering layer of the heart, or
                                  v.            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:
                                   i.            to the chest wall, either muscle or ribs, or
                                  ii.            through the diaphragm, or
                                 iii.            to any organ contained in the mediastinum (esophagus, trachea, thymus,
                                                 blood vessels), or
                                 iv.            to the spine, or
                                  v.            across to the pleura on the other side of the chest, or
                                 vi.            through the heart lining or into the heart, or
                                vii.            to the brachial plexus (nerves leading to the arm), or
                               viii.            to lymph nodes outside that side of the chest, or
                                 ix.            spread to other organs through the bloodstream.

Butchart Staging System
This system is based mainly on the extent of the primary tumor mass, and divides mesothelioma into stages I through IV.

• 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: 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 have disease in them.
• Stage IV: disease has 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.