Lung cancer is a growth of abnormal cells inside the lung. These cells reproduce at a much faster rate than normal cells. The abnormal cells stick together and form a cluster or growth, known as a tumour. If the abnormal cells began growing in the lung, this is known as a primary lung tumour.
Cancers that begin in the lungs are divided into 2 main types, non-small cell lung cancer and small cell lung cancer, depending on how the cells look under a microscope.
Non-small cell lung cancer, which is the most common type of lung cancer, accounting for about 80 per cent of all lung cancers, affects the cells that line the main bronchi (tubes into the lungs) and smaller airways. Non-small cell lung cancer generally spreads to distant organs at a slower rate than small cell lung cancer.
Small cell lung cancer, which tends to start in the middle of the lungs and is very strongly associated with cigarette smoking, accounts for about 20 per cent of all lung cancers.
Cigarette smoking is the major cause of lung cancer. Up to 90 per cent of cases of the disease are caused by smoking. However, it is not known why one smoker develops lung cancer while another does not. Although unusual under the age of 40, the risk of developing lung cancer increases significantly after the age of 50. The younger a person is when they first commence smoking, the higher the risk of developing lung cancer.
Other causes of lung cancer include environmental (passive) smoking, although the risk is less than active smoking, and occupational exposure to asbestos. The greater the exposure to asbestos at work, the greater the risk of lung cancer. This risk is even greater among smokers. Additional occupational exposures possibly associated with lung cancer include contact with the processing of steel, nickel, chrome, exposure to arsenic and coal gas, and exposure to radiation.
The incidence and death rates of lung cancer among men is falling along with a declining incidence of smoking among men. Lung cancer incidence and death rates among women have risen, reflecting a growing incidence in the number of women smoking cigarettes in the past few decades.
Lung cancer is very difficult to detect at an early stage, although all tumours are present for some time before they are discovered. Sometimes lung cancer is discovered by chance, such as when a chest X-ray is done before surgery for another condition.
Common symptoms of lung cancer include:
If the lung cancer has already spread to other parts of the body, it may cause symptoms such as bone pain and headaches.
If lung cancer is suspected, several tests can be performed to determine whether or not the disease is present. The doctor will ask about past and current health, and smoking and work history, and will conduct a physical examination. The doctor may then recommend a series of initial tests for lung cancer, including a chest X-ray, CT scan, and sputum test. Your doctor may also refer you to a specialist for a bronchoscopy (a special test that allows your doctor to look inside your lungs and take tissue samples, or biopsies) and further scans. Some of these tests can show whether the cancer has spread to other parts of the body.
The type of lung cancer treatment provided depends on many factors, including:
There are various treatment options for lung cancer, each with different aims.
When treatment is recommended, it is important to know whether the intention of this treatment is to cure or just to relieve symptoms. This decision is based on the cell type, where the cancer cells are located, and whether there has been any spread beyond the lung tissue itself. It is also important to ask about risks or side effects of any proposed treatment so that the correct decisions regarding appropriate treatment can be made.
The outcome depends on the cell type, how far it has spread, and the person's level of health and suitability for surgery. If small deposits of non-small cell lung cancer are surgically removed prior to spreading, there is a 5-year survival rate of about 80 per cent.
For more advanced non-small cell lung cancer limited to the chest, the 5-year survival rate, even with a combination of surgery, radiotherapy and chemotherapy, drops to less than 50 per cent.
The survival rate with widespread non-small cell lung cancer that has spread outside the chest is far less satisfactory. Small cell lung cancer also tends to have a poor outcome. Of people with limited disease, about a quarter can be cured with a combination of chemotherapy and radiotherapy. Unfortunately, because most small cell lung cancers have spread by the time they are diagnosed, cure rates are very low.
As many cancers have already spread at the time of diagnosis, only about 15 per cent of all lung cancers are cured. The aim of treatment in incurable lung cancer is to reduce symptoms and maintain quality of life, allowing terminal lung cancer patients to maintain their dignity and be cared for at home or in a hospice.
Essentially, the results of treatment are best when the cancer is detected and treated early. People who have surgery in the early stages of lung cancer have the best chance of cure.
Last Reviewed: 26 June 2009