The stages of a cancer

• What staging is
• Why staging is important
• Staging systems
• The 'TNM' staging system
• Number systems

Staging is a way of describing the size of a tumour 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 from where it started.

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 and hormone therapy 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 'positive lymph nodes'. The cells have broken away from the original tumour and got trapped in the lymph nodes. But we can't always tell if they've got any further. In this situation, doctors usually suggest 'adjuvant' treatment. This means treatment alongside the treatment for the main primary tumour. The aim is to kill any cancer cells that have broken away from the primary tumour.

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

• Doctors have a common language to describe tumours
• 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.

'TNM' stands for Tumour, Node, Metastasis. This system can describe the size of a primary tumour, whether there are lymph nodes with cancer cells in them and whether the cancer has spread to a different part of the body. The system uses numbers to describe the cancer

• 'T' can be 1 to 4, with '1' being a small tumour and '4' a large one
• 'N' can be 0 to 3, with '0' meaning no positive lymph nodes and '3' many positive nodes
• 'M' is either 0 or 1, with '0' meaning the cancer has not spread and '1' meaning that it has spread

These usually have a scale of 1 to 4 (or sometimes A to D). '1' typically means a small tumour that has not spread and no positive lymph nodes. '4' would mean that the cancer had spread to other major organs in the body.

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