The staging of lung cancer
Once lung cancer has been diagnosed, your doctor will want to determine the stage or extent of the disease. This involves finding out how large the tumour is and whether the cancer is limited to the lungs or if it has spread to other parts of the body (the presence of metastases) or to lymph nodes. The tests your doctor performed to diagnose lung cancer, such as a CAT scan and MRI, help determine the stage of disease.
Why is it important for your doctor to determine the stage of your lung cancer?
When you and your doctor know how large the cancer is and whether it has spread either to nearby structures (e.g. the lymph nodes) or further away (metastasised), together you can choose the best treatment option.
The most common system used to describe stages of lung cancer is the TNM staging system, which stands for Tumour, Node, and Metastasis. Your doctor will determine the T, N, and M status of the tumour. The first step is assigning a T or tumour stage.
Tumour
T is for Tumour Stage
The tumour stage or T stage is used to describe the size and location of the primary (or main) tumour in the lungs. There are six different T stages and your doctor will determine the one that best describes the tumour. The six T stages are:
Tumour
|
Stages |
T0
|
No evidence of a primary tumour |
T1
|
Tumour is less than 3 cm |
T2
|
Tumour is either more than 3 cm or is found in parts of the lung, such as the main bronchus or visceral pleura, or causes atelectasis or obstructive pneumonitis in a part of the lung |
T3
|
Any size tumour that touches areas near the lung, such as the chest wall or diaphragm, or causes atelectasis or obstructive pneumonitis in the entire lung |
T4
|
Any size tumour that touches other parts of the chest, such as the heart or trachea, or multiple tumours in the same lung lobe or a tumour that causes a malignant pleural effusion |
TX
|
Primary tumour cannot be evaluated or was only proven by a positive sputum cytology but not visualized by imaging or bronchoscopy. |
Node
N is for Regional Lymph Node Stages
After the primary tumour is staged, the regional lymph nodes located in and around the lungs are evaluated to determine the N stage. There are five different N stages and your doctor will determine the one that best describes the cancer. The five N stages are:
Regional
|
Lymph Node Stages |
N0
|
No cancer found in the regional lymph nodes |
N1
|
Spread to lymph nodes located near or around a bronchus, or nodes in the lung caused by growth of the primary or main tumour, both occurring on the same side of the lung as the tumour (ipsilateral) |
N2
|
Spread to lymph nodes located near the mediastinum, or where the windpipe branches into the left and right bronchi, both occurring on the same side of the lung as the tumour (ipsilateral) |
N3
|
Spread to lymph nodes found on the opposite side of the lung as the primary tumour (contra lateral); or nodes are found in the neck |
NX
|
Regional lymph nodes cannot be evaluated. |
Metastasis
M is for Metastasis Stages
After the T and N stages are identified, the last step is determining the M stage, which is used to describe the presence or absence of metastases or cancer in other parts of the body such as the bone or the brain. No-lymph nodes are covered by the N bit of the classification. There are three different M stages and your doctor will determine the one that best describes the cancer. The three M stages are:
MO - No distant metastases found
M1 - Distant metastases found
MX - Distant metastasis cannot be evaluated
Lung cancer can also be staged using a system of Roman numerals, from Stage I disease to Stage IV disease. Stage I is the earliest stage of lung cancer and Stage IV is the latest or most advanced stage of the disease.
The table below describes the TNM system and the corresponding overall numerical stage, as well as the most common treatments used as initial therapy for each stage.
Numerical Stage
|
TNM Stage
|
Most Common Initial Treatments |
IA
|
T1 N0 M0
|
Surgery or radiation used alone or together |
IB
|
T2 N0 M0
|
Surgery or radiation used alone or together |
IIA
|
T1 N1 M0
|
Surgery or radiation used alone or together |
IIB
|
T2 N1 M0
T3 N0 M0 |
Surgery or radiation used alone, together or with chemotherapy |
IIIA
|
T1 N2 M0
T2 N2 M0 T3 N1 M0 T3 N2 M0 |
Radiation alone or with chemotherapy |
IIIB
|
Any T
N3 M0 T4 Any N M0 |
Chemotherapy alone or with radiation; or palliative care |
IV
|
Any T
Any N M1 |
Chemotherapy alone or with radiation; or palliative care |
The treatment of lung cancer and its prognosis are largely based on the stage of lung cancer at diagnosis. For example, patients diagnosed with Stage IA disease are generally treated with surgery and have a 5-year survival rate of about 50%. Patients diagnosed with stage IV disease are generally treated with chemotherapy and have a lower 5-year survival rate. Other factors, such as your general state of health and type of lung cancer, also affect treatment options and prognosis (outlook).
Another factor that may affect prognosis is the grade of your tumour. Tumour grade measures how abnormal the cells are in your tumour. Cells within the tumour are compared to normal cells under a microscope. The more they look and function like normal cells the lower the grade, and the more abnormal they look and function the higher the grade. In general, the higher the grade (more abnormal cells) the more aggressive, or fast growing, the cancer is.
