Staging is the process of finding out how far a cancer has spread. Your treatment and prognosis (outlook) depend, to a large extent, on the cancer's stage.

Staging is based on the results of the physical exam, biopsies, and imaging tests (CT scan, PET scan, etc.), which are described in the section, "How is malignant mesothelioma diagnosed?"

Since pleural mesothelioma occurs most frequently and has been studied the most, it is the only mesothelioma for which a staging system exists.

The TNM staging system

The system most often used to describe the growth and spread of pleural mesothelioma is the American Joint Committee on Cancer (AJCC) TNM staging system. The TNM system describes 3 key pieces of information:

• T indicates the extent of spread of the main (primary) tumor.

• N describes how much the cancer has spread to nearby (regional) lymph nodes. Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections.

• M indicates whether the cancer has spread (metastasized) to other organs of the body. (The most common sites are the pleura on the other side of the body, the lungs, and the peritoneum.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors. The numbers 0 through 4 indicate increasing severity.

T groups

T1: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm. It may or may not have spread to small spots on the pleura covering the lung as well.

T2: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm, and has grown into at least one of the following:

• a large area of the pleura lining the lung
• the diaphragm
• the lung itself

T3: Mesothelioma involves either the right or left pleura lining the chest wall, lung, or diaphragm and has grown into at least one of the following:

• the first layer of the chest wall
• the fatty part of the mediastinum (space between the lungs)
• a single place in the deeper layers of the chest wall
• the pericardium (outer covering layer of the heart)

T4: Mesothelioma involves either the right or left pleura lining the chest wall, lung, or diaphragm and has grown into at least one of the following:

• the deeper layers of the chest wall, including the muscle or ribs
• through the diaphragm and into the peritoneum
• any organ in the mediastinum (esophagus, trachea, thymus, blood vessels)
• the spine
• across to the pleura on the other side of the chest
• through the heart lining or into the heart itself
• the brachial plexus (a collection of nerves leading to the arm)

N groups

N0: No spread to lymph nodes.

N1: Spread to lymph nodes within the lung and/or around the area where the bronchus enters the lung (hilar lymph nodes) on the same side as the mesothelioma.

N2: Spread to lymph nodes around the carina (point where the windpipe branches into the left and right bronchi) and/or in the space behind the breastbone and in front of the heart (mediastinum). Affected lymph nodes are on the same side as the primary tumor.

N3: Spread to lymph nodes near the collarbone on either side, and/or spread to hilar or mediastinal lymph nodes on the side opposite the primary tumor.

M groups

M0: No spread to distant organs or areas.

M1: The cancer has spread to distant sites. This can be to distant lymph nodes or to other organs.

Stage grouping for pleural mesothelioma

Once the T, N, and M categories have been assigned, this information is combined in a process called stage grouping to assign an overall stage of I, II, III, or IV. The stages identify tumors that have a similar prognosis and thus are treated in a similar way. Patients with lower stage numbers tend to have a better prognosis.

Stage I

T1, N0, M0: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm. It may or may not have spread to small spots on the pleura covering the lung as well. It has not spread to the lymph nodes or to distant sites.

Stage II

T2, N0, M0: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm and has grown into a large area of the pleura lining the lung, the diaphragm, or the lung itself. It has not spread to the lymph nodes or to distant sites.

Stage III

There are 2 combinations of categories that make up this stage.

T1 or T2, N1 or N2, M0: Mesothelioma involves either the right or left pleura lining the chest and may or may not have grown into the pleura lining the lung, the diaphragm, or into the lung itself. It has spread to lymph nodes in the chest on the same side as the tumor. It has not spread to distant sites.

T3, N0-2, M0: Mesothelioma involves either the right or left pleura lining the chest and has grown into the first layer of the chest wall, the fatty part of the mediastinum, a single place in the deeper layers of the chest wall, or the outer covering layer of the heart. It may or may not have spread to lymph nodes in the chest on the same side as the tumor but has not spread to lymph nodes near the collarbone or on the opposite side of the chest. It has not spread to distant sites.

Stage IV

There are 3 combinations of categories that make up this stage.

T4, any N, M0: Mesothelioma involves either the right or left pleura lining the chest and has spread into the deeper layers of the chest wall (including the muscle or ribs), through the diaphragm and into the peritoneum, into any organ in the mediastinum, into the spine, across to the pleura on the other side of the chest, through the heart lining or into the heart itself, or into the brachial plexus. It may or may not have spread to lymph nodes. It has not spread to distant sites

Any T, N3, M0: The tumor is of any size. It has spread to lymph nodes near the collarbone on either side and/or to hilar or mediastinal lymph nodes on the side opposite the primary tumor. It has not spread to distant sites

Any T, any N, M1: The mesothelioma is of any size and may or may not have spread to the lymph nodes. It has spread to distant sites.

Resectable versus unresectable cancer

The TNM system divides mesotheliomas into several groups that help give doctors an idea about a person's prognosis (outlook). But for treatment purposes, doctors often use a simpler system based on whether these cancers are likely to be resectable (where all visible tumor can be removed by surgery) or unresectable.

In general terms, most stage I and some stage II and III mesotheliomas are potentially resectable, but there are exceptions. Resectability is based not only on the size of the tumor, but also on the subtype (most doctors believe only epithelioid tumors are potentially resectable), where it is located, and whether or not a person is healthy enough to have surgery.

Even for resectable mesotheliomas, in most cases there are cancer cells that cannot be seen that are left behind after surgery. For this reason, many doctors advise using other forms of treatment (radiation therapy and/or chemotherapy) along with surgery when possible.

Other prognostic factors

Stage is an important factor in determining a patient's prognosis, but other factors also play a role. Some factors linked to longer survival times include:

• good performance status (being able to perform normal tasks of daily life)
• younger age
• epithelioid subtype
• not having chest pain
• no significant weight loss
• normal levels of a substance in the blood called LDH
• normal red blood cell counts, white blood cell counts, and blood platelet counts

Survival statistics for mesothelioma

Mesothelioma is a serious disease. By the time the symptoms appear and cancer is diagnosed, the disease is often advanced. But regardless of the extent of the cancer, it can be very hard to treat.

In the medical literature, average survival times for people with mesothelioma have ranged between 4 and 18 months, depending on the study. About 10% of people with mesothelioma live at least 5 years after being diagnosed.

Because these cancers are not common, it is hard to find accurate survival rates based on the TNM stage of the cancer. As a general rule, survival times are likely to be higher for people with mesotheliomas that can be operated on than for those with cancers that have metastasized. Other prognostic factors, such as those listed above, may also affect survival.

There are some other important points to keep in mind when looking at survival statistics such as the numbers above.

These numbers are derived from patients treated at least several years ago. Improvements in treatment since then mean that the survival statistics for people now being diagnosed with these cancers may be higher.

Survival statistics can sometimes be useful as a general guide, but they may not accurately represent any one person's prognosis. A number of factors other than the type and extent of the cancer may also affect outlook, including a person's general health and the response of the cancer to treatment. Your doctor is likely to be a good source as to whether the numbers above may apply to you, as he or she is familiar with the aspects of your particular situation.

Last Medical Review: 03/17/2009
Last Revised: 03/17/2009