Carcinogens like cigarette smoke are chemicals that cause cancer. These chemicals come in contact with the airways and air sacs by inhalation.

Cancer then starts in the cells lining the airways and air sacs and may spread to neighbouring lymph glands. Unfortunately, the prognosis and survival of lung cancer is comparatively worse than other cancers. There is also no reliable screening test to detect early lung cancers. 

How common is Lung Cancer?

Lung cancer is one of the commonest cancers in Singapore. Between 1988 and 1992, over 4,000 people in Singapore were diagnosed with lung cancer. Smokers have a 15 to 25 times greater risk of contracting lung cancer than nonsmokers.

Lung cancer in a person under the age of 40 is rare. The incidence increases rapidly after age 50.

Cigarette smoking is the main cause of lung cancer. It is responsible for about 90% of all lung cancers. The risk of cancer increases with greater the number of cigarettes smoked per day and the greater the number of years a person has been smoking. Smoking pipes and cigars also increases the risk of lung cancer. Spouses of smokers have a 35% higher risk of developing lung cancer than spouses of nonsmoking persons.

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

Only 70% of Asian Chinese females who get lung cancer are smokers and this group may have other, yet unidentified risk factors.
 

•  Cough
•  Shortness of breath
•  Bloodstained sputum
•  Lung infections are also common in persons with lung damage.

If the suspicion of cancer is high, a CT scan may be arranged. Subsequent tissue sampling may require a bronchoscopy. In this examination, a fiber-optic tube, about 5-6 mm in diameter, is introduced through the nose and into the lung under local anaesthesia. The patient 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.

Once cancer is diagnosed, scans of other organs such as liver, brain and bone may be performed to determine if the cancer has spread.

Clinical examinations, x-rays and pathology reports all help the medical team decide what the stage of an individual case of lung cancer may be. Then, the appropriate course of treatment will be 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 are involved? Have all the involved lymph glands been removed at surgery?
• What is the type of lung cancer? Small cell lung cancers vary in prognosis and treatment from non-small cell lung cancers. 
• What other organs are involved? 
• If the person has other underlying medical illnesses, surgery may not be possible even if the cancer was small and at an 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 a high risk.

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 (doctor who looks at tissues under the microscope) sees on microscopic examination of the tissue that had been removed.

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

Surgery is the preferred treatment. The cancer and part of the surrounding normal lung tissue is removed, together with neighbouring lymph nodes. Subsequent chemotherapy with or without radiotherapy may often be used to reduce the rate of recurrence.

If surgery is considered too risky because of the person's age or other illnesses, radiotherapy may be given to the cancer and the neighbouring lymph nodes. The exact amount of radiation given has to be decided on an individual basis by the radiation oncologist (doctor who prescribes radiotherapy). Many factors have to be taken into account, such as the person's age, general health, amount of normal lung and the size of the cancer. Radiotherapy may also be combined with chemotherapy.

Sometimes chemotherapy is given first in order to shrink the lung tumour before considering radiotherapy or surgery. This is usually the case if the cancer is too large to be removed by surgery or if the person has other medical problems making surgery too risky. The decision is made after all the doctors involved- the surgeon, medical and radiation oncologists have discussed the individual's case.

Chemotherapy and radiotherapy may be also given to relieve symptoms caused by the cancer. When other therapeutic options have been exhausted, intensive palliative care is provided to alleviate symptoms and keep the patient comfortable. 

Small cell lung cancer tends to spread quickly to other organs, such as the 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 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 medicines will depend on the person's general health and other medical illnesses. 

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

Lung cancer takes 10 to 30 years to develop. The risk increases with each increasing 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 and cervix cancer, heart disease and stroke. Smoking causes lung damage, which may lead to symptoms such as chronic cough, and breathlessness. Smoking can also harm family members and aggravate other lung conditions.