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The stages of a cancer

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This page tells you about cancer staging. There is information about

 

What staging is

Staging is a way of describing the size of a cancer and how far it has grown. When doctors first diagnose a cancer, they carry out tests to investigate the extent of the cancer locally and to see whether it has spread to another part of the body. This is different to the grade of cancer, which describes how similar a cancer cell is to a normal cell.

 

Why staging is important

Staging is important because it usually tells the specialist which treatments you need. If a cancer is just in one place, then a local treatment such as surgery or radiotherapy could be enough to get rid of it completely. A local treatment treats only one area of the body.

If a cancer has spread, then local treatment alone will not be enough. A systemic treatment will be needed as well. Systemic means treating the whole body. Chemotherapy, hormone therapy and other drug treatments are systemic treatments because they circulate throughout the body in the bloodstream.

Sometimes doctors aren't sure if a cancer has spread to another part of the body or not. They look at the lymph nodes near to the cancer. If there are cancer cells in these nodes, it is a sign that the cancer has begun to spread. Cancer doctors call this having positive lymph nodes. The cells have broken away from the original cancer and got trapped in the lymph nodes. But we can't always tell if they have gone anywhere else. 

If cancer cells are found in the lymph nodes, doctors usually suggest adjuvant treatment. This means treatment alongside the treatment for the main primary tumour (chemotherapy after surgery, for example). The aim is to kill any cancer cells that have broken away from the primary tumour.

 

Staging systems

Staging systems are worked out for most types of cancer. The systems are there so that

  • Doctors have a common language to describe cancers
  • Treatment results can be accurately compared between research studies
  • Guidelines for treatment can be standardised between different treatment centres

Two main types of staging systems are used by doctors. The TNM system and number systems. Some cancers have their own staging systems, such as Dukes' staging for bowel cancer.

 

The TNM staging system

TNM stands for Tumour, Node, Metastasis. This system can describe the size of a primary tumour, whether the cancer has spread to the lymph nodes and whether the cancer has spread to a different part of the body (metastasised). The system uses numbers to describe the cancer.

  • 'T' refers to the size of the cancer and how far it has spread into nearby tissue – it can be 1, 2, 3 or 4, with 1 being small and 4 large 
  • 'N' refers to whether the cancer has spread to the lymph nodes – it can be between 0 (no lymph nodes containing cancer cells) and 3 (lots of lymph nodes containing cancer cells)
  • 'M' refers to whether the cancer has spread to another part of the body – it can either be 0 (the cancer hasn't spread) or 1 (the cancer has spread)

Sometimes the letters a, b or c are used to further divide the categories. For example, stage M1a lung cancer (the cancer has spread to the other lung) and stage M1b lung cancer (the cancer has spread to other parts of the body). 

As well as T1 – T4, you can get Tis. This means carcinoma in situ, which is a very small and very early stage cancer. It is such an early stage that it is sometimes called pre-cancer.

The letter p is sometimes used before the letters TNM – for example, pT4. This stands for pathological stage. It means that the stage is based on examining cancer cells in the lab after surgery to remove a cancer.

The letter c is sometimes used before the letters TNM – for example, cT2. This stands for clinical stage. It means the stage is based on what the doctor knows about the cancer before surgery. The stage is based on clinical information from examining you and looking at your test results.

So for example, a small cancer that has spread to the lymph nodes but not to anywhere else in the body may be T2 N1 M0. Or a more advanced cancer that has spread may be T4 N3 M1.

 

Number staging systems

Number staging systems usually use the TNM system to divide cancers into various stages. These usually have a scale of 1 to 4. Less often, the scale is A to D. '1' typically means a small tumour that has not spread and there is no cancer in the lymph nodes. '4' would mean that the cancer has spread to other major organs in the body.

Sometimes doctors use the letters A,B or C to further divide the number categories – for example, stage 3B cervical cancer.

There is information about staging for each type of cancer in the treatment sections of your cancer type

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Updated: 24 July 2013