Small Cell Lung Cancer

According to the American Cancer Society, small cell lung cancer (SCLC) accounts for 10 to 15 percent of all diagnosed lung cancers. Exposure to asbestos is a well-established cause of SCLC, and some 98 percent of those afflicted with the cancer have a history of smoking. It is extremely rare for someone who has never smoked to develop SCLC.

Typically originating in the bronchi near the center of the chest, SCLC is aggressive and spreads quickly throughout the body. In many cases the cancer can disperse from its initial location before presenting any symptoms. If symptoms do arise, they are usually nonspecific and can include an atypical cough, chest pain and weight loss.

There are three varieties of small cell lung cancer:

• Small cell carcinoma (oat cell cancer)
• Mixed small cell / large cell carcinoma
• Combined small cell carcinoma

The majority of small cell lung cancer cases are oat cell type. Although the cancer cells are smaller in size compared to non-small cell lung cancers (NSCLC), which make up 85 to 90 percent of all lung cancers, SCLC grows quickly and produces large tumors. In the early stages of development these tumors can rapidly spread to other parts of the body such as the lymph nodes, bones, the liver, adrenal glands and the brain. Unfortunately, surgery is rarely an option with SCLC because of this factor. Doctors instead rely upon chemotherapy that attacks cancerous cells all throughout the body.

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Risk Factors

Smoking cigarettes is the leading risk factor for lung cancer by far. Between 85 and 90 percent of all lung cancer deaths are tobacco-related, and the figures for SCLC are likely to be even higher. Typically, the longer you smoke and the more packs per day, the greater the risk. Regardless of your age or how long you have been a smoker, quitting immediately may lower your risk of developing SCLC and improve your overall lifespan.

Another important risk factor for SCLC is asbestos, which is responsible for 4 percent of all annual lung cancer diagnoses in the United States. Workplace exposure to asbestos (specifically in mines, mills, textile plants, shipyards and places where asbestos insulation is used) greatly increases the chance of developing lung cancer. Furthermore, smoking while exposed to asbestos creates a synergistic effect where the risk of developing cancer is notably higher than adding the risks of both factors individually.

Primary Symptoms

Small cell carcinomas tend to be centrally located and usually cause irritation or obstruction of the patient's major airways. At the time of presentation, fewer than 5 percent of patients have a small primary tumor that triggers no symptoms whatsoever. In the majority of cases, however, patients diagnosed with SCLC may exhibit the following symptoms:

• Persistent, worsening cough
• Chest pain
• Coughing up blood
• Loss of weight or appetite
• Shortness of breath
• Wheezing

Spreading of SCLC to distant organs may cause:

• Bone pain
• Neurologic changes (headache, numbing of limbs, dizziness or seizures)
• Jaundice
• Lumps near surface of the body

It is important to understand that most of the symptoms listed above are more likely to be caused by conditions other than SCLC. Regardless, any of these problems are a cause for concern, so you should notify your doctor immediately in order to find and treat the cause as soon as possible.

Associated Syndromes

When medical conditions cause a specific group of symptoms they are often referred to as syndromes. For example, small cell and non-small cell lung cancers located in the upper portion of the lungs can damage a nerve that passes from the upper chest into the neck. This results in Horner syndrome, which can lead to severe shoulder pain, a drooping eyelid, a smaller pupil and reduced sweating on one side of the face. Common syndromes associated specifically with small cell lung cancer include:

• Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH): This condition occurs when the cancer cells produce a hormone which causes the kidneys to retain water. Salt levels in the blood are reduced causing symptoms like restlessness, fatigue, nausea and muscle weakness.
• Ectopic Cushing Syndrome: Cancer cells sometimes produce a hormone which causes the adrenal glands to secrete cortisol. In turn, symptoms such as weight gain, drowsiness and high blood pressure often arise.
• Neurologic problems: In some cases SCLC can cause the body's immune system to attack parts of the nervous system, causing a variety of problems. One common problem is known as Lambert-Eaton syndrome (LEMS) and results in muscle weakness of the limbs. In many cases LEMS is the first symptom of the lung cancer.

Staging and Prognosis

The treatment options and chances of recovery for SCLC predominantly depend on the stage of the disease at the time of diagnosis. Other important factors to consider are patient age, gender and overall health. There are several approaches to staging small cell lung cancer, but doctors usually prefer a two-stage classification:

• Limited stage: Cancer is limited when confined to one lung and potentially the lymph nodes of the chest cavity's affected side. Approximately 33 percent of SCLC patients exhibit limited disease at the time of diagnosis.
• Extensive stage: Cancer enters the extensive stage when it spreads away from the lungs into other parts of the body including the liver, bones, adrenal glands and brain. This is common in about 67 percent of SCLC patients at the time of diagnosis.

When diagnosed early on in the limited stage SCLC can be treated with a combination of chemotherapy and radiation. Only a very small percent of SCLC cases are treated with surgery due to the disease's rapid growth and high probability of spreading. When treated immediately, about 25 percent of patients will survive at least two years. Unfortunately, once the cancer has reached the extensive stage the survival rate is very low. Fewer than 5 percent of treated patients will live for five years or more if the cancer has spread. In these cases doctors offer palliative treatments that aim to relieve symptoms instead of curing the cancer.