Making an educated treatment decision about how to manage lung cancer begins with the determination of the stage, or progression, of the disease. The stage of the disease tells doctors how big the cancer is and how far it has spread in the body.
The tests and scans that patients with lung cancer undergo to diagnose their cancer provide some information about the stage of the cancer. Sometimes it is not possible to be certain about the stage of a cancer until after surgery.
Different types of lung cancer are staged differently.
Non-small cell lung cancer (NSCLC) staging
For NSCLC staging, physicians can use the TNM system to stage lung cancer. Tumor (T) describes the size of the primary tumor, lymph node (N) indicates whether the cancer is present in the lymph nodes and metastasis (M) refers to whether the cancer has spread to other parts of the body, typically the liver, bones or brain.
According to the American Cancer Society, a number (0-4) or the letter X, is assigned to each factor. A higher number indicates increasing severity. The letter X means the information could not be assessed. For instance, a T1 score indicates a smaller tumor than a T2 score. Once the T, N, and M scores have been assigned, an overall stage is assigned.
Occult stage NSCLC. Cancer cells are found in sputum, but no tumor can be found in the lung by imaging tests or bronchoscopy, or the tumor is too small to be checked.
Stage 0 NSCLC (T0): Also known as carcinoma in situ, this is another early stage lung cancer that has not spread beyond the lungs. In this stage, only a few layers of cancer cell have been discovered in one area, and have not broken through the top lining of the lung. Since the cancer has not spread, the prognosis is similar to that of the occult stage, with a five-year survival rate of 60-80 percent.
Stage1 NSCLC (T1): The cells look very much like normal cells. They tend to be slow-growing and are less likely to spread than higher grade cancer cells. They are called low grade. Cancer may be present in the underlying lung tissues, but the lymph nodes remain unaffected.
Stage 2 NSCLC (T2): The cells look more abnormal and are more likely to spread. This grade also is called moderately well-differentiated, or moderate grade. The cancer may have spread to nearby lymph nodes or into the chest wall.
Stage 3 NSCLC (T3): The cells look abnormal. They tend to grow quickly and are more likely to spread. They are called poorly-differentiated or high grade. The cancer is continuing to spread from the lungs to the lymph nodes or to nearby structures and organs, such as the heart, trachea and esophagus.
Stage 4 NSCLC (T4): The cancer has metastasized throughout the body and may now affect the liver, bones, or brain.
Distant metastasis (M) are categorized as follows:
M0: No distant metastasis
M1: Distant metastasis
M1a: Separate tumor nodule(s) in a contralateral lobe, tumor with pleural nodules, or malignant pleural (or pericardial) effusion
M1b: Distant metastasis (in extrathoracic organs).
Small cell lung cancer (SCLC) staging
SCLC accounts for less than 20 percent of lung cancers and is usually caused by tobacco smoking. It frequently starts in the bronchi, then quickly grows and spreads to other parts of the body, including the lymph nodes. There are two stages of SCLC:
Limited stage: The cancer is found in one lung, and sometimes in nearby lymph nodes.
Extensive stage: The cancer has spread to the other lung, the fluid around the lung (the pleura), or to other organs in the body.
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