What Is Staging?
Staging is the process of figuring out where cancer is in a patient’s body, how much cancer is there, and how much it has spread from the location of the original tumor. The stage designation does not change, even as the cancer grows and spreads, or shrinks with treatment.
This is hard to understand, but it is a consistent approach that doctors use to describe cancer in patients. As an example, consider a patient that has been diagnosed with stage II mesothelioma. A few months later it has spread to the lymph nodes. This patient would now be described as having stage II mesothelioma with lymph node metastasis, rather than changing the stage to III or IV.
The Importance of Staging
The staging of mesothelioma can be thought of as a more detailed investigation or diagnosis of cancer in an individual. It gives all members of a medical team the information about where and how the cancer has spread in a patient. It is a way of communicating this important information that impacts care planning. For instance, stage IV cancers are nearly impossible to treat with surgery while a stage I cancer may be cured through surgery.
The staging also helps doctors estimate a prognosis, which is important for patients to understand. Data collected from previous patients can help determine the average life expectancy of different types of cancer in each stage.
Factors Used to Stage Mesothelioma
The process of staging any cancer, including mesothelioma, involves examining a patient using various diagnostic techniques. Doctors and specialists use imaging scans of the patient’s body as well as examination of biopsied tissue samples to describe several features of the cancer that can then be used to stage it:
- The location of the original tumor and any other tumors
- The cell type, such as sarcomatoid or epilthelioid
- The size of the tumor or tumors
- If the cancer cells have spread to the lymph nodes
- If the cancer cells have spread to another part of the body
- The tumor grade, which is a description of the extent of abnormal qualities of its cells
The TNM Staging System
In order to communicate information about a patient’s cancer from one medical professional to another, it is important that cancers are staged according to set guidelines. There are multiple systems and guidelines used for staging, but the TNM system is the most widely used, including for mesothelioma.
The TNM system uses three main factors for describing the stage. The T stands for tumor and refers to the primary tumor. N stands for nodes and is a description of the extent to which the cancer has spread to the lymph nodes. M stands for metastasis and describes the extent to which the original tumor has spread and invaded other tissues or organs in the body.
The T designation in staging mesothelioma describes the original tumor:
- TX means the tumor could not be assessed.
- T0 is no evidence of a primary tumor.
- T1 is a primary tumor in the pleura on just one side of the chest and possibly along the diaphragm.
- T2 is a primary tumor found in the pleura on one side of the chest, but also on the pleura lining the diaphragm and the lung. It has spread into either the diaphragm or the lung.
- T3 is a primary tumor that includes every location in T2 and has also either invaded the chest wall, fatty tissues, or the pericardium.
- T4 is a primary tumor that has invaded even further, into the esophagus, trachea, thymus, spine, or to the pleura on the other side of the chest.
The N factor describes the extent to which the cancer has invaded the lymph nodes:
- NX means the lymph nodes couldn’t be examined.
- N0 means there has been no spread to the nodes.
- N1 means that the cancer has spread to lymph nodes within or near the lung on the same side as the primary tumor.
- N2 means the cancer has spread to lymph nodes farther out, but on the same side of the chest as the primary tumor.
- N3 means it has spread to nodes on either side of the chest.
M describes whether or not original tumors have metastasized, or spread to more distant parts of the body. M0 means that no metastasis a has been detected, and M1 indicates that there has been any degree of metastasis. There are no other indications under this heading.
Stage I Mesothelioma
A combination of T1, N0, and M0 is considered stage I mesothelioma. This stage describes a cancer in which the tumors are only in the pleural tissue. There has been no spread to the lymph nodes and no metastasis.
Life expectancy for stage I mesothelioma is longer than for the other stages, but unfortunately few people are able to get a diagnosis this early. Stage I mesothelioma does not usually cause symptoms severe enough to lead to a diagnosis. If it is caught this early, aggressive treatment with surgery, chemotherapy, and radiation is typical.
Stage II Mesothelioma
A combination of T2, N0, and M0 is considered to be stage II mesothelioma. At this stage a patient may have some spread of the primary tumor, but it has still not metastasized or invaded the lymph nodes. Symptoms at stage II are still pretty mild and may be mistaken for other conditions. Treatment at this stage is similar to stage I. The survival rate for stage II mesothelioma is about 19 months.
Stage III Mesothelioma
Stage III mesothelioma may be a combination of T1 or T2, N1 or N2, and M0. It may also be T3, N0 through N2, and M0. It is during stages III and IV that most people finally get a diagnosis. At this point the cancer has spread to various parts of the pleura and other tissues close to the original tumor, such as the lungs or diaphragm. It may also have spread to nearby lymph nodes. There are more symptoms at this stage, including significant breathing difficulties and chest pains. Surgery may or may not be an option as treatment at stage III.
Stage IV Mesothelioma
A combination of any T designation with N3 and M0 is considered stage IV mesothelioma, as is a combination of any T, any N, and M1. Many patients with mesothelioma are not diagnosed until the cancer has reached stage IV. There is either extensive cancer in the lymph nodes or actual metastasis, which makes it very difficult to treat. People at this stage are not expected to live longer than a year and most cannot be treated surgically. Chemotherapy, radiation, and palliative treatments may extend life and make the patient feel more comfortable.
Resectable, Unresectable, and Metastatic Mesothelioma
There are other ways to categorize mesothelioma that are broader and less detailed than staging. For instance, a cancer may be categorized as metastatic if it has been seen to have spread to distant parts of the body from the primary tumor. This is essentially another way of saying that the cancer is stage IV.
Mesothelioma may also be described as resectable or unresectable. This refers to whether or not surgery can be used as a treatment. In most stage I, II, and III mesothelioma patients, surgery is an option to try to remove all or some of the tumor, either to attempt to cure it or to slow the progression of the disease. These cancers are resectable. If surgery is not an option, usually because the cancer has metastasized, it is categorized as unresectable.
In addition to the descriptions of T, N, and M, other factors may be considered and used to describe mesothelioma. These may or may not affect the assigning of a stage. One additional factor is tumor grade. The grade describes how abnormal the cells of the tumor appear when inspected under a microscope. The more abnormal the cells the more likely the cancer is to grow and spread quickly. Grade is usually given as a number from one to three.
Alternative Staging Systems
Most doctors currently use the TNM system to stage mesothelioma, but there are some alternatives, including the Butchart system. This is an older system for mesothelioma and it was designed to identify patients that were good candidates for aggressive and potentially curative treatment. It also uses designations of stage I through IV. The Brigham system is an additional staging system that also makes use of the designations I through IV.
The staging of mesothelioma is a crucial part of diagnosing it completely, as is determining whether or not the cancer has metastasized. The description of stage helps medical teams figure out what the best treatments are for a particular patient and gives that patient an estimated outlook for the future and how helpful the treatments are likely to be. If you have been diagnosed with mesothelioma, be sure that you get a thorough assessment of the stage and seek a second opinion if you are not satisfied.
Page Medically Reviewed and Edited byLuis Argote-Greene, M.D.
Luis Argote-Greene is an internationally recognized thoracic surgeon. He has trained and worked with some of the most prominently known thoracic surgeons in the United States and Mexico, including pioneering mesothelioma surgeon Dr. David Sugarbaker. He is professionally affiliated with University Hospitals (UH). His areas of interest and expertise are mesothelioma, mediastinal tumors, thoracic malignancies, lung cancer, lung transplantation, esophageal cancer, experimental surgery, and lung volume reduction. Dr. Argote-Greene has also done pioneering work with video-assisted thoracoscopic surgery (VATS), as well as robotic assisted minimally invasive surgery. He has taught the procedures to other surgeons both nationally and internationally.