The predominant staging system for cancer in general involves four steps, with stage 1 being a cancer that has been diagnosed early and is localized, and stage 4 being an advanced form of the disease that has metastasized, or moved to remote parts of the body in addition to the original tumor. For small cell lung cancer (SCLC) the staging structure that is usually employed has only two steps and is much simpler than the four step protocol. However both systems can be applied and sometimes are.
Two Stage Protocol for Small Cell Lung Cancer
SCLC is different from the more common forms of lung cancer that involve non-small cell tumors, in that it spreads rapidly and moves to remote parts of the body very early in the development process. Staging us used to dictate both severity of the disease and the treatment that is appropriate; usually the treatment for small cell lung cancer does not involve surgery. Chemotherapy and radiation are used for treatment regardless of degree to which the disease has advanced, so the staging protocol can be relatively simple.
The two lung cancer stages for small cell lung cancer are limited, and extensive. Limited means that the disease remains on one side of the body (in one lung) and if it has metastasized, has done so only in nearby lymph nodes. Limited is the term for the early stage of the disease. Extensive SCLC is the advanced stage; the cancer has spread to remote areas of the body, to the other lung, and possibly to other organs. Two thirds of all diagnosed cases of SCLC have reached the extensive stage by the time the disease is discovered.
The TNM Four Stage System
The American Joint Committee on Cancer developed an elaborate staging system that involves assigning values to three important characteristics and then combining those values to arrive at a numerical state. The “T” refers to defining the scope of the malignant tumor(s). The “N” is an analysis of the degree to which the cancer has impacted the lymph nodes throughout the body. The “M” has to do with the degree to which the disease has spread, or metastasized.
Once those analyses are completed they are combined to identify which numerical classification is appropriate.
- 1A means the tumor is smaller than 3cm across; the cancer has not reached the membrane lining the lung, and has not spread to the lymph nodes.
- 1B can have one of more of the following features: the tumor is between 3cm and 5 cm across; the cancer has reached the visceral pleura which is the membrane lining the outer lung; the tumor is partially blocking the airways.
- 2A has three combinations of the three categories that may describe the patient’s condition: the tumor remains small but the cancer has gotten into the lymph nodes on the same side of the body; the conditions are similar to those in 1B but the cancer has advanced to the lymph system; the tumor is between 5cm and 7cm and is impacting the airways or the bronchus.
- 2B can be for a large tumor that has grown into the bronchus and is the lymph nodes on the same side of the body; or it is larger than 7cm, has grown into the chest wall, or has blocked an airway enough to result in a collapsed lung.
- 3A is for a tumor of any size that has reached the area where the windpipe splits into the two bronchi leading to the lungs; or it is a large tumor that has also metastasized to the chest wall or has spread to the lymph nodes in and around the lung.
- 4 defines a cancer that has moved to the other lung; has developed malignancy in the fluid surround the lung (the pleural fluid); or it has spread to remote parts of the body such as the liver or the brain.
These are simplified definitions of the TNM steps. Because SCLC is usually diagnosed at the extensive stage and because treatment options are the same regardless of the degree to which the disease has developed, the simpler two stage system is adequate for diagnosis and treatment.