Cancer staging systems are used as a way of labeling how far the disease has progressed. There are various cancer staging systems which can be used for mesothelioma but they all are based on the same basic ideas: stages are given numbers with the lowest number having the least amount of progression and the higher numbers the most progression. Mesothelioma progression can be evaluated by various factors including the size of the cancerous masses, how far it has spread to other organs, and whether lymph nodes have been affected. The stage of mesothelioma can be changed after treatment.
Mesothelioma staging is very important during diagnosis. While the stage of the mesothelioma will not alter its progression, it is an indicator of the patient’s prognosis. Patients in the early stages of mesothelioma have better prognoses than those in the later stages. Most importantly, mesothelioma staging will determine the course of treatment which is used. In the earlier stages of mesothelioma, patients typically have many more treatment options available to them, such as surgery. In the last stages of mesothelioma, patients may not have any promising treatment options available, and treatments focus more on quality of life issues.
There are three primary systems used for staging mesothelioma: Butchart Staging System, TNM Staging System, and Brigham Staging System. These systems can be used for staging any type of mesothelioma. However, typically only pleural mesothelioma is staged and there is no medically established staging system for peritoneal mesothelioma.1 However, medical researchers are developing new staging systems for malignant mesotheliomas like the novel tumor node metastasis staging system based on prognostic parameters for diffuse malignant peritoneal mesothelioma.2
Butchart Staging System
The Butchart staging system was the first staging system used for diagnosing mesothelioma. It was developed in the 1970s by Doctor Eric G. Butchart. It is the simplest method of staging mesothelioma and is still often used for this reason.
- Stage 1: In stage 1 of the Butchart system, pleural mesothelioma is located only in the pleura and may also be in the lung, pericardium, or diaphragm. The mesothelioma is only located on one side rather than in both lungs.
- Stage 2: The pleural mesothelioma has spread out of the lungs and into the chest wall or esophagus. The cancer may have also metastasized to both sides of the chest and the heart and also to the lymph nodes of the chest.
- Stage 3: During the third stage, the pleural mesothelioma has metastasized from the lungs and chest and invaded the abdominal area. The cancer may have also affected lymph nodes out of the chest area.
- Stage 4: In this final stage of mesothelioma, the cancerous growths have spread to parts of the body far from the origin and the cancer is being carried in the blood.
TNM Staging System
TNM stands for Tumor, lymph Nodes and distant Metastasis. Each of these three aspects is given its own classification under the system.
Tumor Classification:
TX: The tumor cannot be evaluated
T0: There is no evidence that a tumor is present
Tis: Abnormal cells are present and are not cancerous but could become so
T1, T2, T3, T4: Indicate the size and metastasis of the tumor
Lymph Nodes Classification:
NX: The lymph node cannot be evaluated
N0: The cancer has not spread into the lymph nodes
N1, N2, N3: The extent the cancer has spread to surrounding lymph nodes
Distant Metastasis:
MX: The distance of metastasis cannot be evaluated
M0: The cancer has not metastasized
M1: The cancer has metastasized
The TNM Staging System can also utilize other parameters like the grade of the cancerous cells, whether the cancer has invaded veins, and the success of surgery to remove tumors.
Brigham Staging System
The Brigham staging system was designed by Doctor David Sugarbaker. The system takes its name from the Brigham and Women’s Hospital at Harvard. This system is particularly useful when surgical removal of mesothelioma is believed possible.3 It consists of four stages.
- Stage 1: The cancer has not spread to the lymph nodes. It can be surgically removed.
- Stage 2: The cancer has spread to the lymph nodes but can still be surgically removed.
- Stage 3: The cancer has spread to surrounding parts of the body and may have also spread to their lymph nodes. The cancer cannot be removed with surgery.
- Stage 4: The cancer has metastasized far from the site of origin.
Staging is not a cut and dried process. Not only is there no consensus among doctors on the system to use, but the final determination depends on your medical team’s opinion within parameters. The lack of consensus means you may not get the same staging across medical institutions. However, it’s the best method established to date for determining survival potential and best treatment options and, the TNM system especially, is being refined as more data is collected.3
References
1 The stages of mesothelioma (2010) Retrieved from Cancer Research UK – CancerHelp UK at: http://cancerhelp.cancerresearchuk.org/type/mesothelioma/treatment/the-stages-of-mesothelioma
2Yan TD, Deraco M, Elias D, Glehen O, Levine EA, Moran BJ, Morris DL, Chua TC, Piso P, Sugarbaker PH (May 2011) A novel tumor-node-metastasis (TNM) staging system of diffuse malignant peritoneal mesothelioma using outcome analysis of multi-institutional database, Cancer, v117:9, 1855-63.
3 Richards, W. G. (Summer 2009) Recent advances in mesothelioma staging, Semin Thorac Surg v21:2, 105-10.
