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Lung cancer is one of the five most commonly diagnosed cancers in Australia. It usually occurs in people over the age of 65 years, but can affect younger adults. Lung cancer causes more deaths than any other type of cancer in Australia, and has a 5-year survival rate of about 14%.
There are two types of lung cancer: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Small cell lung cancer accounts for 10%-15% of all lung cancers. Compared with NSCLC, it tends to grow and spread more quickly, and has often reached other parts of the body by the time it is diagnosed.
The two subtypes of SCLC are named for the types of cells the cancer develops in, and how these look under the microscope. These are small cell carcinoma (also called oat cell cancer), and combined small cell carcinoma.
While the cause of SCLC cannot be identified in every case, people who develop this cancer are usually smokers, or have been smokers in the past.
The main risk factors associated with developing lung cancer include:
• tobacco smoking (cigarettes, pipes or cigars)
• exposure to second-hand smoke (smoke breathed out by others)
• a family history of lung cancer
• being infected with HIV (human immunodeficiency virus)
• being treated with radiation therapy to the chest area
• being exposed to air pollution, radon (a radioactive gas), asbestos, or certain other chemicals.
In a small minority of cases, inherited DNA mutations appear to be linked to developing lung cancer. However, in most cases DNA mutations are acquired during a person’s lifetime, and occur as a result of exposure to environmental factors such as tobacco smoke.
Researchers continue to work on improving our understanding of the causes of lung cancer and how it might be prevented. Currently, the most important preventative measure is avoiding tobacco smoke.
Lung cancers diagnosed early are usually found by accident, such as when testing for other medical conditions. More often, the cancer is already advanced by the time symptoms appear.
When symptoms do develop, they may include:
• a persistent cough
• blood in the sputum
• shortness of breath
• chest pain
• loss of appetite
• unexplained weight loss
• difficulty swallowing
• swelling in the face and/or veins of the neck.
Aside from taking a medical history and conducting a physical examination, a number of tests may be done to diagnose lung cancer, such as:
• a chest x-ray
• biopsy (removing a sample of lung tissue for examination).
• laboratory testing of samples e.g. sputum, blood, urine
• imaging tests e.g. CT scan/CAT scan
• bronchoscopy (using a scope to look inside of the lungs)
• thoracoscopy (a surgical procedure to look at the organs inside the chest).
Other imaging tests, such as MR I scans, PET scans and bone scans may be done to check how far the cancer has spread.
The process used to determine how far cancer has spread at the time of diagnosis is called staging. Stages for SCLC are called Limited-Stage (when the cancer has spread from the lung to the area between the lungs, and/or to nearby lymph nodes), and Extensive-Stage (when the cancer has spread to other areas of the body).
Treatment for SCLC depends on a number of factors, including the stage of the cancer. In cases of early-stage lung cancer, where the cancer is contained to one lung and nearby lymph nodes only, surgery may be possible. In most cases however, the cancer has already spread by the time it is found, and other treatments are required.
Even if all the cancer seen at diagnosis can be removed by surgery, patients may be given chemotherapy or radiation therapy afterwards to kill any cancer cells left in the body. This is called adjuvant therapy.
Additional treatments used for SCLC include laser therapy (where a laser beam is used to kill cancer cells), and endoscopic stent placement (where a structure called a stent is used to open an airway blocked by abnormal tissue).
In cancer research, new drugs and new combinations of drugs are continually being investigated to make treatments for SCLC more effective. Targeted therapies, such as those that inhibit the formation of blood vessels in tumours (anti-angiogenesis drugs), are being investigated, as are immune therapies including vaccines.
After treatment for lung cancer, follow-up visits are needed at regular intervals into the future. During these visits, tests such as blood tests and CT scans may be done as well as physical examinations, to check for any signs of the cancer returning, as well as any late effects of treatments received.