Understanding Staging Lung Cancer
Staging is the process by which once lung cancer is confirmed, the degree to which the cancer has established itself and how it presents in a patient is categorized. This is essential if an appropriate and effective treatment regime is to be recommended and implemented in a lung cancer patient.
Staging is frequently referred to as “TNM” by oncologists (cancer specialists).
TNM refers to the three main factors used in staging:
• Primary Tumor (T) – whether there is a tumor or tumors which can be established;
• Lymph Nodes (N) – whether the cancer has occurred in the lymph nodes; and
• Metastasis (M) – whether the cancer has spread to or from other parts of the body.
Each of these factors is further assessed to provide more detailed clarification. For instance, where a tumor cannot be located but it is confirmed by the presence of cancer cells, the assessment will be TX.
A detailed explanation follows:
Primary Tumor (T)
TX – no tumor is located but is confirmed by presence of cancer cells
T0 – no evidence of a primary tumor
T1 – primary tumor of less than 3cm and not in the main bronchus
T2 – primary tumor which is any of the following:
• Larger than 3cm
• Is present in the main bronchus or other important parts of the lung
T3 – primary tumor of any size invading surrounding tissue or chest wall
T4 – as T3 but affecting the heart, trachea, great blood vessels – more serious than a T3 tumor
Regional Lymph Nodes (N)
Lymph nodes are small, bean shaped objects which are reservoirs of immune cells and materials vital to protect the body. Regional lymph nodes refers to those lymph nodes in the surrounding vicinity of the lungs.
NX – no assessment
N0 – no regional lymph node metastasis (i.e. the lung cancer has not spread to the lymph nodes)
N1, N2 and N3 – metastasis has occurred to increasing severity
Distant Metastasis (M)
Metastasis refers to the spreading of the cancer to or from other parts of the body. This is important because primary cancer (i.e. cancer which has originated at that location in the lung) is susceptible to treatment by surgery whereas metastasized lung cancer usually is not).
MX – no assessment of distant metastasis
M0 – no distant metastasis has occurred
M1 – distant metastasis has occurred and includes separate tumor(s) in other parts of the lung or body
Allocation of a Stage
After assessment of the tumor, lymph nodes and metastases, a stage is allocated which depends on the findings of how many tumors, where they are located and how they have spread?
The stages are allocated as follows:
Occult carcinoma – TX, NO, MO – cancer is present because of the presence of cancer cells but it cannot be located or assessed. This is not allocated a distinct stage but is classed as an “unknown” or medical wildcard.
Stage 0 – any Tumor, N0 and M0
Stage IA – T1, N0, M0
Stage IB – T2, N0, M0
Stage IIA – T1, N1, M0
Stage IIB – T2, N1, M0 or T3, N0, M0
Stage IIIA – T1-T2, N2, M0 or T3, N1-N2, M0
Stage IIIB – Any T, N3, M0 or T4, any N, M0
Stage IV – Any T, Any N, M1
This is obviously a complicated exercise which may require repeated visits to the hospital and your doctor, but it is vital to effective treatment that this staging process is properly conducted. How well staging is conducted has a direct bearing on survival rates of patients with lung cancer.