The most often used staging system for mesothelioma is the Butchart system. This is also the oldest staging system used. There are four stages which describe extent of the primary tumor mass. Stage I: mesothelioma present in left or right pleura and may involve the diaphragm, pericardium, or lung on effected side. Stage II: mesothelioma has invaded the chest wall or bilateral involvement of the heart, lung, or pleura. This stage may also include lymph node involvement. Stage III: This indicates the diaphragm has been penetrated by the mesothelioma and lymph nodes beyond the chest may now be involved. Stage IV: Distant metastasis is evident. This may involve contralateral lymph nodes, as well as extension of tumor into contralateral pleura or lung tissue. This may also involve direct extension of tumor into abdomen or neck. Other staging systems include the TNM and Brigham staging systems.
T represents the size and spread of the tumor. Mesothelioma in all T stages involves one side of the membrane covering the lungs and lining the walls of the chest known as the pleura.
T1: cancer has spread to the pleura covering the lung;
T2: cancer has spread to the outer lining of the lung, the diaphragm, or the lung;
T3: cancer has spread into the first layer of the chest wall or a spot in the chest wall, the fatty part of the area between the sternum and the spinal column known as the mediastinum, or the outer layer of the heart;
T4: cancer has spread into the chest wall, through the diaphragm, into an organ within the mediastinum, into the spine, across to the opposite pleura, through the lining of the heart or into the heart, or into the nerves leading to the arm.
There are three staging systems in staging mesothelioma, the Butchart System, the TNIM System, and the Brigham System. The oldest and most commonly used staging system is the Butchart System. This system contains four stages and bases the stages on the size of the primary tumor. Below, the four stages of the Butchart System are listed.
Stage I: Mesothelioma is occurring on either side of the pleura (right or left) and may include the diaphragm on that same side.
Stage II: Mesothelioma is occurring in the chest wall or occurring in the heart, esophagus, or bilateral pleura. There may be lymph node involvement at this stage.
Stage III: Mesothelioma is occurring in the diaphragm and into the lining of the peritoneum. There may be lymph node involvement at this stage.
Stage IV: Metastasis has occurred and the mesothelioma has spread through the bloodstream and into other organs.
The choice of radiographic studies and laparascopic investigation to accurately determine extent of disease is under debate. Both gadolinium contrast MRI scans and PET scans have been shown to aid in staging of mesothelioma. Others, however, argue that laparoscopic thorascopy is the most appropriate tool for assisting in staging. Current TNM classification is as follows:
Stage I: Completely resected within capsule of parietal pleura without adenopathy
Stage II: All stage I characteristics with positive resection margins, adenopathy, or both
Stage III: Local extension of disease into chest wall, mediastinum, diaphragm, peritoneum, or to extrapleural lymph nodes
Stage IV: Distant metastatic disease
Prognosis of mesothelioma is extremely poor. Without any treatment, mesothelioma is typically fatal within 4 to 13 months of diagnosis. Regardless of therapeutic approach, treated patients can expect a 6 to 18 month median survival rate. Few patients have survived 5 years after diagnosis.
The TNM staging system for malignant mesothelioma was adopted in 2002. This system utilizes description of the tumor involvement, lymph node involvement, and the presence or not of distant metastasis of the tumor. Staging is then categorized based on the TNM data.
Tx refers to a tumor that cannot be assessed.
T0 is no evidence of primary tumor.
T1 through T4 refer to the extent of tumor invasion in and around the lung structures.
Nx refers to lymph nodes that cannot be assessed.
N0 implies no regional lymph node metastasis.
N1-N3 refers to the anatomical location of lymph node metastasis.
Mx refers to distant metastasis that cannot be assessed.
M0 is no evidence of distant metastasis.
M1 is any distant metastasis present.
Disease stage is then determined as Stage 1A, 1B, Stage II, III, or IV based on the TNM criteria above.
Most recently the TNM staging system has been used to stage mesothelioma. However, historically, the Butchart system was used and now there is also a new staging system which may be increasingly implemented, the Brigham system. The Butchart system describes how extensive the primary tumor is, whereas the TNM system defines cancers by tumor extension, lymph node involvement, and whether there are metastases. The Brigham staging identifies how resectable a lesion may be.Each system has four stages. Generally the first stage is localized disease which is easily resectable and involves no lymph nodes. In stage two, the cancer has spread and may affect lymph nodes, but is often treatable with surgical excision and adjunctive therapies. Stage three is extensive disease, often crossing internal boundaries such as the diaphragm but may still respond to debulking surgery and chemotherapy or radiation. The fourth stage in all of the systems is defined by metastatic lesions.