Lung cancer is a type of cancer that begins in the lungs. In Singapore, it is the third most common cancer diagnosed each year among both males and females. Smokers have the highest risk of developing lung cancer. The risk of lung cancer increases with the duration and number of cigarettes smoked. Once one quits smoking, the chance of developing lung cancer decreases, although it takes years to equal that of a non-smoker. Passive smokers, e.g., non-smoking spouses of smokers and those in the same household, also have an increased risk of developing lung cancer.
Types of lung cancer
There are two major types of lung cancer based on the appearance of cancer cells under the microscope. Treatment decisions are based on which type of lung cancer is present.
The two major types of lung cancer are:
Small cell lung cancer (SCLC): small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer. The prognosis is poor as patients usually present late with the disease that has spread.
Non-small cell lung cancer (NSCLC): this is the most common type of cancer. Non-small cell lung cancer is an umbrella term for several types of lung cancers that behave in a similar way. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
Symptoms of suspected lung cancer
Signs and symptoms of lung cancer typically may not be noticeable in the early stages. One should seek immediate medical attention when any of the following signs or symptoms begin to be of concern to you:
- A cough that lasts more than two weeks
- Chronic cough or “smoker’s cough”
- Coughing up blood (even in small amounts)
- Breathlessness
- Chest pain
- Wheezing
- Hoarseness
- Unexplained weight loss
- Bone/joint pain
- Fatigue
- Headache
- Swelling of face or arms
- Facial paralysis
Diagnosis
If you are worried about any symptoms you may have that may suggest you have lung cancer or any other serious lung condition, it is advisable to consult a lung specialist. The doctor will order a number of tests to look for cancerous cells and rule out other conditions. The first test performed is usually a chest X-ray. If the chest X-ray is abnormal, a chest CT scan will be ordered to clarify the abnormalities seen. Sometimes, the CT scan picks up abnormalities that are not seen on a chest X-ray.
Subsequent tests may include:
Sputum cytology: if you have a cough and are producing sputum, looking at the sputum under the microscope can sometimes reveal the presence of lung cancer cells.
Lung biopsy: a sample of abnormal cells is removed in a procedure called a biopsy. Your doctor can perform a biopsy in a number of ways, including the following:
- Bronchoscopy: a lighted tube is inserted through the nose into the lungs. With it, your doctor is able to examine abnormal areas of your lungs and obtain lung tissue for analysis.
- Mediastinoscopy: an incision is made at the neck, and lymph node samples are taken.
- Needle biopsy: the use of an X-ray or chest CT to guide a needle through the chest wall and into the lung tissue to collect tissue samples.
- Thoracocentesis / Pleural biopsy: this is carried out to drain fluid from the space around the lungs, if cancer has spread to the pleura the membrane that covers the lungs).
A biopsy sample may also be taken from lymph nodes or other areas where cancer is thought to have spread, such as the liver.
Stages of lung cancer
Once lung cancer is diagnosed, the doctor will order tests to determine the stage of your cancer. Staging determines the extent of the disease, specifically if cancer has spread and where it has spread to. To determine the stage of cancer, tests such as CT scans, magnetic resonance imaging (MRI), positron emission tomography (PET), and bone scans may be ordered to look for cancer spread beyond the lung (metastasis).
Non-small cell lung cancer is staged as 1 to 4. Stages 1 and 2 are the early stages, i.e., the cancer is limited to the chest. Stage 3 is also referred to as locally advanced lung cancer, and stage 4 is known as late-stage lung cancer, i.e., cancer has spread to distant sites, e.g. in the bones or brain.
Small cell lung cancer is usually staged as being limited or extensive. The limited stage indicates that cancer is limited to one lung. An extensive stage indicates that cancer has spread beyond one lung.
Treatment
Early-stage lung cancer (stages 1 and 2) is usually managed by surgery. This usually involves removing a lobe of the lung (lobectomy) or the whole lung (pneumonectomy). The doctor will decide if the patient is fit for surgery before it is contemplated. Lung function testing is mandatory before lung cancer surgery is attempted. Routinely, the surgeon samples the lymph nodes during the operation to ensure that microscopic spread has not occurred.
Late-stage lung cancer (stage 4) is usually treated with chemotherapy. One drug or a combination of chemotherapy drugs may be given intravenously or orally. This is done over a period of weeks or months, with breaks in between to allow the body to recover.
Over the past few years, new oral chemotherapy agents that work only in lung cancer patients with genotypic variants have been used. These oral drugs are called targeted therapy and are less toxic and easier to administer. However, they only work in those whose cancer tissues demonstrate genetic abnormalities, e.g., EGFR (epidermal growth factor receptor) and ALK (anaplastic large-cell lymphoma kinase) mutants.
Radiation therapy uses high-powered energy beams, such as X-rays, to kill cancer cells. Radiation therapy can be directed at the lung cancer from outside your body (external beam radiation), or it can be placed inside needles, seeds or catheters and inserted inside the body near cancer (brachytherapy). Radiation therapy can be used alone or with other lung cancer treatments. Sometimes it’s administered at the same time as chemotherapy.
For very small tumours, stereotactic body radiotherapy may be used. This form of radiation aims at many beams of radiation from different angles at lung cancer. Stereotactic body radiotherapy treatment is typically completed in one or a few treatments. Radiotherapy is generally used if cancer has spread to the brain or bones.
The prognosis of lung cancer remains dismal, with a 5-10% of 5-year survival. However, with the advancement of treatment and new drugs, many patients are living longer with lung cancer. Early diagnosis is essential for a better outcome.
