Introduction

Cancer occurs when normal cells undergo a transformation and grow out of control. These cells will form a growth or tumour which is different from the original tissues. Tumour is dangerous because it uses up oxygen, nutrients and invade nearby tissues. This results in damage or loss of normal function of the tissue.

• In the body, tumour can spread to the nearby lymph nodes or to other parts of the body via the blood stream. This process is called metastasis.
• When lung cancer metastasizes, the tumor in the lung is called a primary tumor and the growth in the other part of the body is called a secondary or metastatic tumour.

Some cancers in the lungs arise from other parts of the body. The lung is a common site for metastases. This is not lung cancer. For example, if a prostate cancer spreads via the blood to the lungs, these are metastatic cancers from the prostate and not lung cancer. It destroys normal tissue function. Most metastatic tumours are malignant. This means they spread and destroy tissues surrounding them and can spread to the rest of the body.

Epidemiology

Lung cancer is the leading cause of death in Malaysia. In the year 2007, overall, it is the third commonest cancer after breast and colorectal cancer. In males, it is the first on the list and the fifth in females. In 2006, 2948 lung cancers were reported (1445 in men and 603 in women). Even though the survival rate after a diagnosis of lung cancer is made is 49%, only less than 2% of cancer patients are still alive in 5 years if the cancer has spread to other parts of the body.

Types of Lung Cancer

Lung cancer is usually divided into 2 groups according to its type of cells:

1. Non-small cell lung cancer (NSCLC). There are a few types which are:
   • Adenocarcinoma (30-40%)
   • Squamous cell carcinoma (30%)
   • Large cell carcinoma (10%)
2. Small cell lung cancer (SCLC) (20%). This type is less commonly found. However, the cancer cells grow at a very rapid rate and most of the time spread to other parts of the body at diagnosis.

Other types of cancer found in the lungs are carcinoid and lymphoma. (5%)

Causes of Lung cancer

Most lung cancer is caused by smoking (90%), this includes both active and secondhand smoking.

• Tobacco smoke contains more than 4000 chemical substances, most of them have been identified to cause lung cancer.
• Smoking 20 cigarettes per day increases the risk to 20 to 25 times compared to non-smokers.
• When a smoker quits smoking, the risk of lung cancer is reduced. After quitting for 15 years, the risk of getting lung cancer is the same as non-smokers.
• Cigar and pipe smoking also increase the risk to develop lung cancer.

Other causes of lung cancer are:

• Air pollution from vehicles, factories and others.
• Exposure to asbestos increases the risk of lung cancer to several times higher.  Interaction between tobacco smoke and asbestos increases the risk to 50 times.  Mesothelioma (cancer arising from the lung pleura) is closely related to exposure to asbestos.
• Lung diseases such as tuberculosis and chronic obstructive pulmonary disease also increase the risk for lung cancer.
• Radon/radium (compound derived from uranium) also increases risk for lung cancer.
• Occupational exposure to arsenic, chromium, nickel, aromatic hydrocarbon and ether also increases the risk.

What Are The Symptoms Of Lung Cancer?

You may be asymptomatic or have symptoms such as cough or difficulty in breathing which you may relate to the respiratory system. Symptoms of lung cancer include:

• Cough or unresolving cough. It is well known that smokers experience chronic cough, however a dramatic change in the degree of cough is an important symptom.
• Chest, shoulder and prolonged backache which is worse with inspiration
• Wheezing
• Shortness of breath
• Hoarseness of voice
• Coughing out of blood or haemoptysis
• Loss of appetite and weight
• Excessive lethargy
• Recurrent chest infection or pneumonia
• “Clubbing” of the fingers

When Should You See A Doctor?

It is advised that you see a doctor if the following occurs:

• Symptoms of lung cancer as mentioned above
• Cough or change in character of cough
• Cough with phlegm mixed with blood or coughing out blood/haemoptysis
• Appetite loss
• Weight loss
• Body aches of unknown cause

Seek treatment from a doctor immediately if the following occurs:

• Coughing out massive amount of blood
• Sudden shortness of breath
• Non-resolving chest pain
• Sudden paralysis
• Sudden blurring of vision

Diagnosis of Lung Cancer

After getting a complete history from the patient, a doctor will do a physical examination. Then, investigations are done to confirm the diagnosis.

Investigations done are as follows:

• Blood investigations
• Sputum examination
• Chest X ray: Not all abnormalities in the chest X ray are cancer, for example fibrosis or lung infection or calcium deposition
• Computerised tomography (CT) scan of the thorax – this test is able to visualize the lungs in a three dimensional setting. It  can also measure the size of the cancer, detect spread of the cancer to other organs thus giving a clue as to the stage of the cancer
• Bronchoscopy. This procedure involves a flexible tube which is connected to a video camera. It allows the doctor to visualize the airways and if there is a presence of an abnormality, a biopsy will be taken to confirm the type of lung cancer
• Pleuroscopy. This procedure is done when there is excessive fluid in the pleural cavity which can be caused by the cancer, whether it is a primary or secondary/metastatic. Pleuroscope is a tube which is connected to a camera. Apart from removing excessive fluid for diagnostic purposes, biopsies can also be done to confirm the type of cancer
• Positron Emission Tomography (PET) scan is done to detect cancer and metastases
• Bone scan is not routinely done nowadays with the availability of the above investigations
• Mediastinoscopy is sometimes used for diagnosis and staging. However, it is an invasive procedure
• Lung function tests

Treatment of Lung Cancer

Treatment depends on:

1. Type of cancer
2. Stage of cancer
3. Functional status and lung function of the patient

The principal treatment is:

• Removal of cancer – only if it is at an early stage (stages 1 and 2 usually)
• Chemotherapy
• Radiotherapy
• Combination of chemotherapy and radiotherapy
• Targeted therapy when the cancer cell is found to have an epidermal growth factor receptor (EGFR) mutation. For this type of cancer, oral medication is given which is known as tyrosine kinase inhibitor. Examples are gefitinib and erlotinib. This tablet is taken by the patient once daily.
• Palliative treatment for advanced cancer

Follow-up Treatment

• After removal of an early stage lung cancer by surgery, the risk of recurrence is possible usually within 2 years
• Certain tests are done at regular intervals to detect recurrence

Palliative Treatment

This consists of medical therapy or nursing care to reduce symptoms and morbidity and not to cure the cancer. The main aim is to relieve symptoms. Palliative treatment includes:

• Reduce pain
• Reduce breathlessness
• Reduce anxiety
• Treat insomnia
• Treat depressive illness

This palliative treatment is done so that lung cancer patients can have a good quality of life and are able to do basic daily activities such as performing prayers, light activities etc so that the patient does not feel left out from their relatives and community.

Prevention of Lung Cancer

At present, there is no cost effective method to detect early lung cancer and patients usually present at a late stage. Thus, the most effective method to prevent lung cancer is to reduce exposure to tobacco smoke whether active or passive/secondhand smoke. To those who are still smokers, it is advised to quit smoking. Exposure to other substances as mentioned above is also advised.

References

1. Kementerian Kesihatan Malaysia. Malaysia cancer statistics: data and figure Peninsular Malaysia 2006 (online) 2006 (cited 2009 Dec 17); (137 pages). Available from: URL:http://www.moh.gov.my/opencms/export/sites/default/moh/report/Cancer/MalaysiaCancerStatistics-2006.pdf
2. National Cancer Registry Malaysia (2007)
3. eMedicinehealth