Lung cancer

Lung cancer is a malignant lung disease primarily caused by cigarette smoking. It often has no obvious symptoms until the disease is quite advanced and has a low rate of survival.

Treatment for lung cancer mainly involves surgery and chemotherapy. Radiation therapy and targeted drug therapies may also be used.

In recent years lung cancer has been the most common cause of death from cancer among men and women in New Zealand, accounting for nearly 20% of all cancer deaths (ahead of bowel/colorectal cancer, breast cancer, and prostate cancer).

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).

Causes

The development of lung cancer is strongly associated with cigarette smoking — approximately 80% of lung cancers are due 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 most lung cancers are linked to tobacco smoking, not all smokers go on to develop lung cancer and lung cancer can occur in people who have never smoked or been exposed to second-hand smoke. These observations suggest 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 and other cancer-causing substances such as arsenic and chromium (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 computed tomography (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:

• Blood tests
• Imaging studies (chest x-rays; CT, PET and bone scans)
• Bronchoscopy (to look inside the airways and take tissue samples, i.e. 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).

Laboratory analysis of cells from biopsy samples will determine the type of lung cancer and imaging studies reveal the stage of the cancer.

Staging of lung cancer

The 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:

Non-small-cell lung cancer

• 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.

Small-cell lung cancer

• Limited-stage: cancer confined to the area of the chest
• Extensive-stage: cancer that has spread to other parts of the body.

Treatment

Treatment 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

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

Radiation therapy, which uses high-powered energy beams to kill cancer cells, may be used for both NSCLC and SCLC. The aim is to destroy cancer cells without damaging too many normal cells. Radiation therapy 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

Chemotherapy drugs are used for both NSCLC and SCLC to kill fast-growing cancer cells.

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.

Targeted therapy

Molecular-targeted therapies usually cause less harm to normal cells than do chemotherapy or radiation therapy. Tyrosine kinase inhibitors are small-molecule drugs that work inside cancer cells to block signals that cancer cells need to grow and divide.

Monoclonal antibodies are man-made immune system proteins that block the growth and spread of cancer by interfering with specific molecules involved in tumour growth and progression.

Some molecular-targeted drug therapies only work if a person's cancer cells have certain genetic mutations. Laboratory mutation testing is available to determine if a molecular-targeted therapy drug will work in a particular person.

Immunotherapy

Immunotherapy drugs use a patient's immune system to fight their cancer by boosting, directing, or restoring the body's natural anti-cancer defences.

Prevention

The most effective measure that can be taken to prevent the development of lung cancer is to not start smoking and to quit smoking if already a smoker. Reducing exposure to passive smoking is also an effective method of prevention.

Although a person’s risk of lung cancer increases with the length of time and number of cigarettes they have smoked, quitting smoking, even after many years of smoking, can substantially reduce the chances of developing lung cancer.

Taking precautions to protect yourself from exposure to toxic chemicals in the workplace, e.g. wearing required safety equipment such as a face mask, is also an important lung cancer prevention measure.

Further information

The 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 (0800 226 237). Information can also be obtained from the Cancer Society website: www.cancernz.org.nz.

Lung Foundation New Zealand is an independent organisation that promotes healthy lungs and early detection of lung disease. It provides patient resources and support. The Lung Foundation’s website is www.lungfoundation.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 or text 4006. Information can also be obtained from the Quit Group website: www.quit.org.nz.

References

Lung Foundation NZ (2017) Lung cancer basics (Pamphlet PDF). Auckland: Lung Foundation New Zealand. https://lungfoundation.org.nz/wp-content/uploads/2017/02/Lung-Cancer-Basics.pdf
Ministry of Health (2017). Cancer: Historical summary 1948–2017 (Report). Wellington: New Zealand Government Ministry of Health. https://www.health.govt.nz/publication/cancer-historical-summary-1948-2017 [Accessed: 21/11/20]
O’Toole, M.T. (Ed.) (2017). Lung cancer. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MO: Elsevier.
Tan, W.W. (2020). Non-small-cell lung cancer (Web Page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/279960-overview [Accessed: 21/11/20]
Tan, W.W. (2020). Small-cell lung cancer (Web Page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/280104-overview [Accessed: 21/11/20]

Last reviewed: December 2020

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