The stage of a cancer is a term used to describe its size, position and whether it has spread beyond where it started in the body. Knowing the extent of the cancer helps the doctors to decide on the most appropriate treatment.

Generally cancer is divided into four stages:

• Stage 1 small and localised
• Stages 2 or 3 has spread into surrounding structures
• Stage 4 has spread to other parts of the body

If the cancer has spread to distant parts of the body, this is known as secondary cancer (or metastatic cancer).

The staging is different for small cell and for non-small cell lung cancers.

Small cell lung cancers are divided into just two stages. This is because small cell lung cancer often spreads outside the lung quite early on. Even if the doctor cannot see any spread of the cancer on your scans, it is likely that some cancer cells will have broken away and travelled through the bloodstream or lymph system.

To be safe, small cell lung cancers are usually treated as though they have spread, whether any secondary cancer can be seen or not.

The two stages of small cell lung cancers are:

Limited disease – the cancer cells can be seen only in one lung, in nearby lymph nodes, or in fluid around the lung (known as a pleural effusion).

Extensive disease – it is clear that the cancer has spread outside the lung, within the chest area or to other parts of the body.

Non-small cell lung cancer is usually divided into four stages.

Stage 1 cancer is very localised and has not spread to the lymph nodes. This stage is divided in two:

• Stage 1A the cancer is no bigger than 3cm in size.
• Stage 1B the cancer is larger than 3cm, or it is growing into the main airway of the lung (bronchus). The cancer may also have spread to the membrane covering the lung (pleura), or made the lung partially collapse.

Stage 2 non-small cell lung cancer is also divided in two:

• Stage 2A the cancer is small, measuring 3cm or less in size, and nearby lymph nodes are affected.
• Stage 2B the cancer is larger than 3cm and in the nearby lymph nodes,
  OR there is no cancer in the lymph nodes, but the tumour has made the whole lung collapse; or it has grown into the chest wall, the membrane covering the lung (pleura), the muscle layer below the lungs (diaphragm), or the covering of the heart.

Stage 3 is also divided in two:

• Stage 3A the cancer is of any size and has spread into the lymph nodes in the middle of the chest (mediastinum), but not to the other side of the chest.
  OR, the cancer has spread into tissue around the lung near to where the cancer started. This can be into the chest wall, the covering of the lung (pleura), the middle of the chest (mediastinum) or other lymph nodes close to the affected lung.
• Stage 3B the cancer has spread to lymph nodes on either side of the chest or above either collar bone.
  OR the cancer has spread into another major structure; such as the gullet (oesophagus), the heart, windpipe (trachea) or a main blood vessel.
  OR there are two or more tumours in the same lung.
  OR there is a collection of fluid containing cancer cells around the lung (pleural effusion).

Stage 4 lung cancer has spread to a distant part of the body, such as the liver, bones or the brain.