The TNM staging system that is used for most forms of cancer has four classifications, with stage 4 designating the most serious or advanced form of the disease. Small cell lung cancer which comprises 15% – 20% of all lung cancer cases, has a simplified two-stage system that is usually employed, but can be matched up with the more widespread four stage system.
Small cell lung cancer (SCLC) has been linked to asbestos exposure and to smoking, two traits that it has in common with the more widely known asbestos cancer, mesothelioma. The two diseases also share other characteristics: they can be aggressive, fast-moving diseases and they are most often diagnosed well after the cancer has begun to grow and spread. SCLC in particular is known for its rapid spread; over two thirds of all cases are not diagnosed until they have reached the advanced stage four category. Because it is so rarely diagnosed early SCLC is staged with a simplified classification system using just two categories: limited and extensive.
Extensive Small Cell Lung Cancer
The advanced stage of SCLC is termed extensive. As with stage four cancer designation, extensive small cell lung cancer has metastasized to distant parts of the body. It gets into the lymph system early in its development, which is how it spreads so rapidly. Many cases of SCLC are diagnosed at the extensive stage because the disease does not exhibit any of the normal lung cancer symptoms until it has spread beyond the lungs. Along with the lymph system extensive SCLC may be found in the liver, the chest wall, the outer lining of the lungs (where mesothelioma usually develops) and in the cranium. The migration to the skull is common enough that some oncologists will irradiate the area even if there is no current evidence of malignancy there.
Stage 4 Lung Cancer Definition
While the first three stages of this protocol have subsets (2A, 2B, 3A, 3b, etc.) there is no such subdivision for stage four lung cancer. For non-small cell lung cancer stage four means one or more of the following: the disease has moved into both lungs; there are malignant cells in the fluid surrounding the lungs, or the fluid surrounding the heart; or the tumor may be any size and may not be in the nearby lymph nodes but has migrated to distant parts of the body such as the liver or brain. The same applies to SCLC, except that it almost always has found its way into the lymph system via the nodes that are in the chest cavity.
Stage 4 SCLC Treatment
Surgery is rarely employed with small cell lung cancer because it is not often diagnosed early enough that surgical removal of the malignant tissue is a realistic possibility. However SCLC is unique among lung cancers in that it is highly sensitive to chemotherapy and/or radiation treatment. Both are very effective. For that reason the treatment protocol for small cell lung cancer is usually the same at all four stages, employing some combination of chemotherapy and radiation. However despite the powerful effect that these therapies can have on SCLC the disease almost always returns within two years, often in just a matter of months.