What are the stages of cancer?
Staging describes the size and severity of the cancer and helps to inform the diagnostic and treatment approach. It offers information on the prognosis of the cancer and helps doctors to evaluate whether a patient will benefit from any clinical trials of new cancer treatments.
The stage of the cancer is determined at the initial diagnosis. The stage does not change even if the cancer continues to grow and spread. Instead, new information gets added on to the initial staging description.
The staging information provided below refers to solid tumours and is consistent worldwide. That enables health care professionals and researchers to exchange information on best treatment options for various types of cancer and to compare results from different clinical trials. Cancers of the central nervous system (brain tumours), childhood cancers and blood cancers are classified according to other, more relevant staging systems.
Stage 0 –non-invasive cancer
Cancer occurs when abnormal cells grow in an uncontrolled way. Stage 0 cancer is a non-invasive, non-life threatening cancer, in which cells grow into a tumour in the location where it started.
Stage 1 – localised cancer
In Stage 1 cancer cells have gained the ability to spread outside the initial location and begin to invade the neighbouring tissue. The cancer remains a single tumour, growing partly in the tissue where it began and partly in connecting tissue. This is a significant step, which enables the cancer to spread and it can become life threatening.
Stages 2 and 3 – regional spread
Once the cancer cells have spread from the initial location to neighbouring tissue, it’s possible that the cells start spreading further. The most common way for cancerous cells to spread is through a lymph (or lymphatic) vessel.
Lymph vessels form the lymphatic system, similar to the cardiovascular system in the body. They carry fluid called lymph. Lymph is filtered in lymph nodes which are distributed widely around the body. The lymphatic system is a vital part of the immune system – the body’s own defence mechanism against any pathogens, and plays a crucial part in the body’s fight against cancer.
When spreading further, a cancer cell may get caught in a lymph node. Sometimes the lymph node gets rid of the cancerous cell and sometimes the cancer cell divides and forms a lump in the lymph node. It can then continue to multiply and grow in the node.
In Stages 2 and 3 the cancer has spread to the region around the original tumour but has not yet spread to other parts of the body. Cancer can also start in the lymph nodes (e.g. lymphoma), which will then be classified as the cancer’s primary location.
Stage 4 – distant spread
Stage 4 means that cancer cells have spread to other organs or parts of the body. When they break away from the initial location, cancerous cells travel through the bloodstream, or the lymphatic system, to another part of the body where they start multiplying again. This process is known as metastasis.
Cancer that forms as a result of spreading from the primary site is referred to as metastatic or secondary cancer.