What is lung cancer?Lung cancer results from abnormal growth of cells in the lining of the lungs, leading to the growth of a malignant tumour.
There are two main types of lung cancer – small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) – which differ in terms of their appearance under a microscope, how they grow and spread to other parts of the body and how they are treated. Approximately 85% of all lung cancers are NSCLC.
Lung cancer is usually fatal – the overall survival rate is about 17% at five years after diagnosis. The reason for the low rate of survival is that lung cancer tends to spread (metastasize) rapidly to other parts of the body very early after it first forms, (i.e. before it is diagnosed).
CausesThe development of lung cancer is strongly associated with cigarette smoking – approximately 90% of lung cancers are attributable to tobacco use. Pipe and cigar smoking can also cause lung cancer, but the risk is not as high as with cigarette smoking. Tobacco smoke contains more than 4,000 chemical compounds, many of which are cancer-causing (carcinogens). Passive smoking, i.e. the inhalation of tobacco smoke by non-smokers who live or work with smokers, is also an established risk factor for the development of lung cancer.
Although the majority of lung cancers are linked to tobacco smoking, not all smokers go on to develop lung cancer suggesting that genetic susceptibility (i.e. indicated by a family history of the disease) may play a role in the development of lung cancer. Other causes of lung cancer include air pollution (from vehicles, industry, and power generation) and inhalation of asbestos fibres (usually in the workplace).
Signs, symptoms, and diagnosis
Symptoms of lung cancer are varied and warning signs are not always obvious. Some people who get lung cancer display no symptoms until the cancer is discovered during a routine chest x-ray or CT scan. In people who do display symptoms, these may include the following:
- Persistent cough and hoarseness
- Shortness of breath, wheezing, and chest pain
- Blood-streaked sputum
- Chest pain
- Frequent episodes of bronchitis or pneumonia
- Weight loss, weakness, and fatigue.
A wide range of diagnostic tests and procedures are used to diagnose lung cancer, including:
- taking a patient history
- physical examination
- blood tests
- imaging tests (chest x-rays; CT, PET and bone scans)
- bronchoscopy (to look inside the airways and take biopsies)
- cytological studies of sputum and bronchial washings (to detect cancer cells in phlegm and lung fluids)
- biopsy (sampling of lung tissue with a special biopsy needle or during surgery to see if it is cancerous).
Staging of lung cancerThe stage of a lung cancer refers to the extent to which the cancer has spread to other parts of the body. Staging helps to determine how the cancer should be treated. Although lung cancer can spread to any organ in the body, the liver, brain, and bones are the most common sites. The two types of lung cancer are staged differently. A simplified overview of staging is as follows:
Stage I: cancer that is confined to the lung
Stage II: cancer that is confined to the chest
Stage III: cancer that is confined to the chest but with larger and more aggressive tumours than at stage II
Stage VI: cancer that has spread to other parts of the body.
Limited-stage: cancer confined to the area of the chest
Extensive-stage: cancer that has spread to other parts of the body.
TreatmentTreatment for cancer involves a combination of surgery to remove cancer cells, and chemotherapy and radiation therapy to kill cancer cells. Lung cancer is incurable unless complete surgical removal of the tumour cells can be achieved.
Surgery is the most effective treatment for lung cancer but is limited to cancers that have not spread beyond the lungs i.e. stage I, II and III NSCLC and in some patients with limited stage NSCLC.
Radiation therapy, which uses high-powered energy beams to kill cancer cells, may be used for both NSCLC and SCLC and is a good option for people who are not suitable for surgery or who refuse surgery. It can also be used after surgery to kill any cancer cells that might remain.
Chemotherapy, which involves giving drugs to kill cancer cells, is used for both NSCLC and SCLC. Chemotherapy drugs may be given alone or in combination with surgery or radiation therapy. Chemotherapy is the treatment of first choice for SCLC since it has usually spread extensively in the body by the time it has been diagnosed.
Also used in the treatment of lung cancer are molecular-targeted therapies. These are drugs (gefitinib, nivolumab and erlotinib) or monoclonal antibodies (cetuximab, bevacizumab) that block the growth and spread of cancer by interfering with specific molecules involved in tumour growth and progression. They are used in some patients with NSCLC that does not respond to standard chemotherapy. Molecular-targeted therapy drugs are often used in combination with standard chemotherapy drugs.
PreventionThe most effective measure that can be taken to prevent the development of lung cancer is to quit smoking. Reducing exposure to passive smoking is also an effective method of prevention.
Further informationThe Cancer Society of New Zealand operates a phone service staffed by specialist nurses to support patients diagnosed with cancer, including lung cancer, as well as their friends and families. The Cancer Information Helpline Service can be contacted on 0800 CANCER (226 237). Information can also be obtained from the Cancer Society website: www.cancernz.org.nz.
The Quit Group, a charitable trust funded by the Ministry of Health, runs smoking cessation programmes in New Zealand. The Quit Group operates the free telephone support service Quitline and can be contacted on 0800 778 778. Information can also be obtained from the Quit Group website: www.quit.org.nz.
ReferencesMinistry of Health (2013). Cancer: New registrations and deaths 2013 (Report). Wellington: New Zealand Government Ministry of Health. http://www.health.govt.nz/system/files/documents/publications/cancer-new-registrations-deaths-2013-nov16.pdf
O’Toole, M.T. (Ed.) (2013). Lung cancer. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Tan, W.W. (2017). Non-small cell lung cancer (Web Page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/279960-overview [Accessed: 02/12/17]
Tan, W.W. (2017). Small cell lung cancer (Web Page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/280104-overview [Accessed: 02/12/17]
Last reviewed December 2017