Once lung cancer is diagnosed and the type of lung cancer is identified, your doctor needs to determine whether or not the cancer has spread and, if so, how much the cancer has spread. This is called “staging” and is determined during diagnostic testing.
It is important to know about your stage of lung cancer as this will help you and your doctor plan the best treatment path for you.
An internationally agreed staging system called “TNM” staging is followed in lung cancer. Both non-small cell lung cancer and small cell lung cancer are staged using the TNM staging system, though treatment decisions for small cell lung cancer are also based on its classification of limited or extensive stage (see below, Staging of small cell lung cancer).
The descriptors of the TNM staging system are:
T stands for TUMOUR — and indicates where the primary tumour is located and how big it is.
N stands for NODES — and indicates whether the cancer has spread to lymph nodes and where the affected lymph nodes are located.
M stands for METASTASIS — and indicates whether the cancer has spread beyond the lung to the other lung structures such as the pleura or to other parts of the body.
Each of these TNM descriptors include staging definitions. The definitions help to clarify the exact characteristics of lung cancer. Definitions include:
Also called occult stage. The tumour is often too small to be seen on the results from imaging devices, such as an x-ray or computed tomography (CT) scan. However, cancer cells may be found in mucus coughed up from the lungs.
Cancer cells are found only in the primary tumour within the lung. This means that the cancer has not gown through the top lining of the lung and that there is no lymph node involvement or involvement to other parts of the body.
Cancer cells are limited to the lung. Tissue around the lung remains normal. Depending on the tumour size, stage I is divided into IA and IB.
Cancer has spread to nearby lymph nodes or the lining of the lungs. Depending on the tumour size, stage ll is divided into IIA and IIB.
Cancer has spread to the lymph nodes in the centre of the chest between the heart and lungs (the mediastinum) or has grown into the chest wall or the outer lining that surrounds the heart (the pericardium). Blood vessels in this area may also be affected. Or, cancer is found in the lymph nodes on the opposite side of the chest where the tumour fist developed. Cancer may also have spread to the lower neck. Depending on the tumour size, stage III is divided into IIIA and IIIB
Cancer cells have spread beyond the lung and chest area to other parts of the body, such as the bones, liver, kidneys and brain.
Staging of small cell lung cancer
Though guidelines recommend TNM staging of small cell lung cancer, because small cell lung cancer is often not visualised on imaging tests as a discrete entity like non-small cell lung cancer, it is often also classified into two categories:
- Limited disease: small cell lung cancer is detected in only one lung and the surrounding lymph nodes.
- Extensive disease: small cell lung cancer that has progressed further than limited stage disease.
Ask your healthcare team for more details about tumour staging and how it may affect your choices for treatment.