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Lung Cancer

Causes and Risks
Treatment Options
Frequently Asked Questions
National Cancer Centre Singapore
Contributed by National Cancer Centre Singapore


What is Lung Cancer?

Lung Cancer is cancer that starts in the lungs. The lungs are located in the chest. They help you breathe. When you breathe, air goes through your nose, down your windpipe (trachea), and into the lungs, where it spreads through tubes called bronchi. Most lung cancer begins in the cells that line these tubes (bronchi).

The two main types of lung cancer are: 
        • Non-small cell lung cancer (NSCLC) which is the most common type of lung cancer. 
        • Small cell lung cancer makes up about 10% of all lung cancer cases.

These types are diagnosed based on how the cells look under a microscope.

How common is Lung Cancer?

Lung cancer is the number 1 killer in males and 2nd in females in Singapore. Between 2009 and 2013, there was an average of 1311 people in Singapore diagnosed with lung cancer yearly. The great majority were smokers. The risk of lung cancer in a smoker is 15 to 25 times more than for a non-smoker. More recently, we have increasingly recognized a group of lung cancer in patients who have never smoked, and a proportion of cases are related to Epidermal Growth Factor Receptor mutations.

Age of Onset

Most persons diagnosed with lung cancer are older than 40 years of age. However, the disease may begin before this age range.

Causes and Risks

Cigarette smoking is the main cause of lung cancer. It is responsible for more than 90% of the cases of lung cancers. The risk of lung cancer is greater with the increased number of years of smoking and the increased number of cigarettes smoked per day. Pipe, cigar and marijuana smoking also increase the risk of lung cancer. Spouses of smokers have a 35% higher risk of developing lung cancer compared to spouses of non-smoking persons. The risk to children of smokers is not yet accurately identified.

Exposure to certain workplace chemicals such as asbestos, coal gas, chromium, nickel, arsenic, vinyl chloride, and mustard gas increases the risk of lung cancer.


Symptoms and Signs of Lung Cancer

Cigarette smoking causes lung damage even in the absence of cancer. The symptoms associated with lung damage are cough and shortness of breath. There may be occasions when there is production of blood stained sputum even when there is no cancer. Lung infections are also common in persons with lung damage. Dilation of the air spaces, or emphysema, is reported to be an especially common complication of smoking in Chinese persons. Lung cancer usually develops in the presence of lung damage. The symptoms and signs of lung cancer may be indistinguishable from lung damage caused by cigarette smoking. Occasionally, lung cancer is diagnosed incidentally when a pre-employment or routine chest x-ray is performed.


Diagnostic Tests

Any persistent cough or change in the nature of the cough, the appearance of blood-stained sputum, or unexplained breathlessness should prompt a person to seek medical advice. Often chest x-rays are important in the first diagnosis of lung cancer. Sputum may be sent for testing for cancer cells or infections, such as tuberculosis, which is not uncommon in Singapore.

If the suspicion of cancer is high, a bronchoscopy may be arranged. In this examination, a fiber-optic tube about 7mm in diameter is introduced through the nose and into the lung under light-sedation and local anaesthesia. You will be able to breathe normally during the procedure which lasts 15 to 30 minutes. Small pieces of tissue can be painlessly removed for further examination to diagnose cancer. Some management decisions in lung cancer (especially pertaining to targeted therapies), require specific genetic tests to be done on cancer cells from your biopsy sample.

Once cancer is diagnosed, computerised tomography (CT) scans of the chest and liver may be performed to determine if the cancer has spread to other organs, such as the liver or adrenal gland, which is just above the kidneys on both sides. Occasionally, bone scans and CT scans of the brain are also required.

A lung function test, which involves blowing into a large cylinder, may be performed pre-operatively to determine the lung function prior to any surgery discussions.

Treatment Options

Treatment of Lung Cancer

There are two main types of lung cancer; small cell lung cancer and non-small cell lung cancer. The diagnosis is based on what the pathologist (a specialist who looks at tissues under the microscope) sees on microscopic examination of the tissue and after special staining tests have been performed on the tissue.

Small cell lung cancer is more rapidly growing and spreads earlier to other organs as compared to non-small cell lung cancer. About 10% of all lung cancers are small cell lung cancer. Non-small cell lung cancer grows slower than small cell lung cancer and tends to be confined to the lung for a longer period of time.

Treatment of Small Cell Lung Cancer

Small cell lung cancer tends to spread early to other organs, such as liver, bone and brain. Therapy involves early chemotherapy. If the cancer has not spread beyond the confines of one lung, chemotherapy combined with radiotherapy has been shown to have better results than just chemotherapy alone.

Chemotherapy is given over a period of 4 to 6 months. There is usually mild nausea or vomiting, complete hair loss, lethargy or tiredness, and loss of appetite. The exact choice of medicine will depend on the person's general health and other prevalent medical problems.

Prognosis of Lung Cancer

Prognosis means the probable outcome of an illness based upon all the relevant facts of the case. All findings from clinical examination and x-ray investigations and pathology reports are important and must be considered together to decide what the progress of an individual case of lung cancer may be. From this, the appropriate course of treatment can be decided and put into action. The treatment strategy will vary from person to person.

The doctor looks for the following features:

  • The size of the lung cancer is important. The larger the cancer, the more likely the cancer will be inoperable.
  • Which of the neighbouring lymph glands were involved? Were all the involved lymph glands removed at surgery? Which other sites in the body are involved with cancer?
  • Did the pathologist see high risk features such as small cell lung cancer? Small cell lung cancer is a rapidly growing cancer. Very often, the cancer has spread to many other organs at the time of diagnosis. Were other organs involved?
  • If the person has other underlying medical problems, surgery may not be possible even if the cancer was small and considered to be early stage. Lung cancer commonly develops in smokers who have lung damage from their many years of smoking. Smoking also increases a person's risk of heart disease and stroke, which may mean that surgery will be high risk.


Avoid active and secondary tobacco smoke exposure. Screening can help to detect lung cancer.

Frequently Asked Questions

1. I have been smoking for many years? Why should I stop smoking now?

Lung cancer takes years to develop. The risk increases with each year of smoking, and with each cigarette smoked per day. Stopping smoking will reduce the risk of cancer developing. Smoking also increases the risk of other diseases, such as bladder cancer, cervical cancer, heart disease and stroke. Even without disease, smoking causes lung damage which may lead to symptoms such as chronic cough and breathlessness. Smoking can also harm your spouse and family members.

How do I stop smoking? How do I stop a family member from smoking?

Smoking cessation clinics are available at many family practitioner's and polyclinics. Avail yourselves to any of these clinics. Giving a family member support will also help him or her to stop smoking. The Quit Programme has a self-help booklet that will also assist you.

Cancer Resources on the Internet

National Cancer Institute
Cancer Therapies
American Cancer Society
National Centre for Biotechnology Information (NCBI)
American Cancer Society
American Lung Association
Lung Cancer Resources Library
Cancer Information Service (National Cancer Institute, USA) 

Click here for English publication on Lung Cancer

Click here for Chinese publication on Lung Cancer

For further enquiries on lung cancer, please call the Cancer Helpline at (65) 6225 5655 or email to