Cancer staging explained

What is cancer staging?

Cancer staging is the process of documenting the location of your cancer, if it has spread to other parts of the body and which parts of the body it has spread to.

Solid cancers (or tumours), for example breast, lung and bowel cancer, are often staged using the TNM system and this information is then used to determine a stage between I and IV.

Blood cancers such as leukaemia, lymphoma or myeloma are staged differently.

As each cancer uses different staging methods, a particular stage for one type of cancer is not equal to the same stage in another type of cancer. For example, Stage III lung cancer has a different meaning to Stage III non-Hodgkin’s lymphoma.

Staging is done when you are first diagnosed (before any treatment is given), after completion of treatment and at relapse or disease progression.

Why is cancer staging important?

Your doctor uses information gained from staging investigations (such as CT or PET/CT scans) to help plan the best course of treatment for you. The type of treatment you receive may be different based on whether your cancer is detected early or at a more advanced stage.

The stage of a cancer can help predict the likely course the cancer may take and give a guide to the likelihood of treatment success and ultimately the chance of survival.

How is cancer staging done?

A range of different tests are done to determine the stage of the cancer.

These might include:

  • physical examinations
  • blood test and other laboratory tests
  • diagnostic imaging scans (such as x-rays, CT scans or PET/CT scans)
  • biopsies (when a small sample of tissue is removed for testing)
  • genetic testing

What are the different staging systems?

There are different staging systems used to describe different cancers. The most common system to describe solid cancers (for example breast, lung and bowel cancers) is the TNM system.

What is the TNM system?

There are three categories in the TNM system:

  • T = Tumour
  • N = Node
  • M = Metastases

Tumor (T)

This gives information about the cancer or tumour such as its size and location, how deeply it has grown in the location it started in (the primary cancer) and if it has grown into nearby cells in the body. A score from 0 to 4 is given depending on how much the cancer has grown, with a higher number given to a cancer that has grown more deeply. For some types of cancers, a letter is also given to describe this in more detail.

Node (N)

N stands for lymph nodes. These are tiny, bean-shaped organs that help fight infection and are part of the lymphatic system. A number is given depending on whether the cancer has spread to lymph nodes or not.

Metastasis (M)

M stands for metastasis, which is when the cancer has spread to distant parts of the body. If the cancer is M0, it has not spread to distant parts of the body. If the cancer is M1, it has spread to distant organs or cells.

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