The stage of cancer provides information such as the size of the tumor and whether it has spread to other areas in the body. This can help your doctor determine the best treatment for you. The method of staging commonly used is called TNM (Tumour, Node, Metastasis). There is a range of imaging techniques that can be used for staging cancer (e.g. a CT scan).
TNM is defined as follows:
Tumor refers to the size and extent of the main tumor.
Nodal: refers to the spread of cancer, if any, to the local lymph nodes, and how many nodes are involved.
Metastasis refers to the spread of cancer, if any, to other parts of the body, and to what extent.
TNM is classified as follows:
- TX – tumor cannot be measured.
- T0 – the main tumor cannot be found.
- T1, T2, T3, T4 – refers to size &/or extent of the main tumor. The higher the number after the T, the larger the tumor or the more it has grown into nearby tissues. For example, T1 means the tumor is still within the organ or structure in the head and neck, T3 means it has penetrated the walls of the structure & T4 means it has spread to neighboring
- NX – cancer in nearby lymph nodes cannot be measured.
- N0 – There is no cancer in nearby lymph nodes.
- N1, N2, N3 – refers to the number and location of lymph nodes that contain cancer. The higher the number after N, the more lymph nodes that contain cancer.
- MX – metastasis cannot be measured.
- M0 – cancer has not spread to other parts of the body.
- M1 – cancer has spread to other parts of the body.
(TNM Staging, The National Cancer Institute)
However, for simplicity, your doctor may use a number system for staging: Stage 1, 2, 3, 4. This also depends on the extent of the tumor, if it has spread, and how far. This may be further subdivided e.g. Stage 2a, 2b, 2c. Stage 4 is commonly known as the Advanced Stage.