How is malignant mesothelioma staged?
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 physical exams, biopsies, and imaging tests (CT scan,
PET scan, etc.), which are described in the section, “How is malignant mesothelioma
diagnosed?” A staging system is a formal way for doctors and nurses to sum up the extent of a cancer.
Pleural mesothelioma, the most common type, is the only mesothelioma for which a
formal 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 is based on 3 key pieces of information:
• T sums up 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 to which
cancers often spread first.
• 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. Higher numbers mean the cancer is more advanced.
T groups
TX: The main tumor can't be assessed for some reason.T0: There is no evidence of a main tumor (the cancer is found elsewhere instead).
T1: Mesothelioma involves the pleura lining the chest wall on one side of the chest. It
may or may not also affect the pleura lining the diaphragm (the breathing muscle) or the
mediastinum (the space between the lungs). It may also have spread to the pleura
covering the lung.
T2: Mesothelioma involves the pleura lining the chest wall on one side of the chest. It
also involves the pleura coating the diaphragm, the mediastinum, and the lung. It also has
grown into at least one of the following:
• The diaphragm
• The lung itself
T3: The mesothelioma has grown further but may still possibly be removed with surgery.
The tumor involves the pleura lining the chest wall on one side of the chest. It also
involves the pleura coating the lung, the diaphragm, and the mediastinum. It also has
grown into at least one of the following:
• The first layer of the chest wall (called the endothoracic fascia )
• The fatty tissue in the mediastinum
• A single place in the deeper layers of the chest wall
• The surface of the pericardium (outer covering layer of the heart)
T4: The mesothelioma has grown too far to be removed completely with surgery. The
tumor involves the pleura lining the chest wall on one side of the chest. It also involves
the pleura coating the lung, diaphragm, and mediastinum on the same side. It also has
grown into at least one of the following:
• More than one place in 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 (pericardium) or into the heart itself
N groups
NX: The nearby lymph nodes can't be assessed.
N0: No spread to nearby lymph nodes. N1: Spread to lymph nodes within the lung and/or around the area where the bronchus
enters the lung (called hilar or bronchial lymph nodes) on the same side as the main
tumor.
N2: Spread to other lymph nodes on the same side as the main tumor, such as the
subcarinal (around the point where the windpipe branches into the left and right bronchi)
and the mediastinal lymph nodes. Also includes spread to the lymph nodes in the space
just behind the breastbone (called internal mammary lymph nodes) and those near the
diaphragm (called peridiaphragmatic ).
N3: Spread to lymph nodes near the collarbone on either side (supraclavicular lymph
nodes), and/or spread to hilar or mediastinal lymph nodes on the side opposite the main
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 the pleura lining the chest wall on one side of the
chest. It may or may not also affect the pleura lining the diaphragm (the breathing
muscle) or the mediastinum (the space between the lungs). It may also have spread to the
pleura covering the lung (T1). It has not spread to the lymph nodes (N0) or to distant sites
(M0).
Stage II
T2, N0, M0: Mesothelioma involves the pleura lining the chest wall on one side of the
chest. It also involves the pleura coating the diaphragm, the mediastinum, and the lung.
The cancer has also grown into the diaphragm or the lung itself (T2). It has not spread to
the lymph nodes (N0) or to distant sites (M0).
Stage III
Either of the following:
T1 or T2, N1 or N2, M0: Mesothelioma involves the pleura lining the chest on one side,
and may or may not have grown into the pleura lining the lung, the diaphragm, or the
mediastinum. It may also have grown into the muscle of the diaphragm or the lung itself (T1 or T2). It has spread to lymph nodes in the chest on the same side as the main tumor
(N1 or N2). It has not spread to distant sites (M0).
OR
T3, N0 to N2, M0: Mesothelioma involves the pleura lining the chest on one side, and
has grown into the first layer of the chest wall, the fatty tissue in 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
(N0, N1, or N2). It has not spread to distant sites (M0).
Stage IV
Any of the following:
T4, any N, M0: Mesothelioma involves the pleura lining the chest on one side and has
grown into more than one place in 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, and/or
through the heart lining or into the heart itself. It may or may not have spread to lymph
nodes (any N). It has not spread to distant sites (M0).
OR
Any T, N3, M0: The tumor may or may not have grown into nearby tissues (any T). 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 main tumor (N3). It has not spread to
distant sites (M0).
OR
Any T, any N, M1: The mesothelioma may or may not have grown into nearby tissues
(any T). It may or may not have spread to the lymph nodes (any N). It has spread to
distant sites (M0).
Resectable versus unresectable cancer
The TNM system divides mesotheliomas into several stages 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, II, and III mesotheliomas are potentially resectable, but
there are exceptions. Whether or not the cancer can be removed depends not only on how
far the tumor has grown into nearby tissues, but also on the subtype (most doctors believe
only epithelioid and mixed/biphasic 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 use other forms of
treatment (radiation therapy and/or chemotherapy) along with surgery when possible.
Other prognostic factors
Stage is an important factor in predicting a patient’s prognosis (outlook), but other factors
also play a role. Some factors linked to longer survival times include:
• Good performance status (being able to carry out 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
Survival rates are often used by doctors as a standard way of discussing a person's
prognosis (outlook). Some patients may want to know the survival statistics for people in
similar situations, while others may not find the numbers helpful, or may even not want
to know them. If you do not want to read about the survival statistics for mesothelioma,
skip to the next section.
In order to get survival rates, doctors have to look at people who were treated at least
several years ago. Although the numbers below are among the most current we have
available, improvements in treatment since then may result in a more favorable outcome
for people now being diagnosed with mesothelioma.
Survival rates are often based on previous outcomes of large numbers of people who had
the disease, but they cannot be used to predict what will happen in any particular person’s
case. Knowing the type and the stage of a person’s cancer is important in estimating their
outcome. But many other factors, such as a person’s age and overall health and how well
the cancer responds to treatment, can also affect a person’s outcome. Even when taking
these other factors into account, survival rates are at best rough estimates. Your doctor
can tell you if the numbers below may apply, as he or she is familiar with your situation.
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,
mesothelioma 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. But some people live much
longer. Between 5% and 10% of people with mesothelioma live at least 5 years after
being diagnosed. These numbers tend to be better for people diagnosed at a younger age.
Because mesotheliomas 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 longer
for people with mesotheliomas that can be operated on than for those with cancers that
have spread too far to be removed. Other prognostic factors, such as those listed in the
previous section, may also affect survival.