Mesothelioma Stages

After mesothelioma is diagnosed, the next step is to try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer's stage when talking about survival statistics.

How is the stage determined?

Pleural mesothelioma (malignant pleural mesothelioma or MPM), the most common type, is the only mesothelioma that has a formal staging system. These mesotheliomas start in the pleura, which includes the lining of the lungs and the inner lining of the chest wall.

The staging system most often used for MPM is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

• The extent (size) of the main tumor (T): How far has cancer spread in the pleura? Has it spread into other nearby pleura or structures? Can it be removed with surgery?
• The spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?
• The spread (metastasis) to distant sites (M): Has the cancer spread to distant organs, like the bones, liver, the lungs or pleura (lining of the lung) on the other side of the body, or the peritoneum (the lining of the abdomen)?

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced. Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more on this, see Cancer Staging.

Clinical stage vs pathologic stage

MPM typically is given a clinical stage based on the results of a physical exam, biopsy, and imaging tests (as described in How Is Mesothelioma Diagnosed?). If surgery is done, the pathologic stage (also called the surgical stage) is determined by examining the tissue removed during the operation. 

Stages of malignant pleural mesothelioma

The stages of mesothelioma range from I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. And within a stage, an earlier letter (after the number) means a lower stage. Each person with cancer is unique, but cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

The system described below is the most recent AJCC system, effective as of January 2018. It's used only for malignant pleural mesotheliomas. Mesotheliomas starting in other places are less common and do not have formal staging systems. Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand.

The following categories may also be used: 

• TX: Main tumor cannot be assessed due to lack of information.
• T0: There's no evidence of a primary tumor.
• NX: Nearby lymph nodes cannot be assessed due to lack of information. 

Resectable versus unresectable cancer

The TNM system groups mesotheliomas into stages that help give doctors an idea about a person’s prognosis (outlook). For treatment purposes, doctors often use a simpler system, based on whether the cancer is likely to be resectable (where all visible tumor can be removed by surgery) or unresectable (all of the cancer cannot be removed).

In general, most stage I, II, and some stage III mesotheliomas might be resectable, but there are exceptions. Whether the cancer can be removed depends not only on how far the tumor has grown, but also on its subtype, where it’s located, and if the patient is healthy enough to have surgery.

Even for resectable mesotheliomas, in most cases cancer cells that can’t be seen are left behind after surgery. Because of this, many doctors use other treatments (radiation therapy and/or chemotherapy) along with surgery when possible.

Other prognostic factors

Stage is an important factor in predicting a person’s prognosis (outlook), but other factors also play a role. Some factors linked to longer survival times include:

• Still being able to carry out normal daily tasks
• Being younger
• Being female
• Having the epithelioid subtype of mesothelioma
• Having normal levels of LDH in the blood
• Having normal levels of red blood cells, white blood cells, and platelets