Smoking and lung cancer

Smoking is one of the most harmful habits a person can get into. It is a major contributor of several chronic illnesses and lung cancer, so it would be wise to think twice before lighting that cigarette. For many smokers, it is not too late for a lifestyle change and there are now proven ways that can help smokers kick the habit. 

What is lung cancer?

Lung cancer is a type of cancer that begins in the lungs and may spread to other parts of the body, including the lymph nodes, liver, bones, and brain. The lungs may also get affected by cancer cells from other organs; this is referred to as metastasis.

The leading cause of lung cancer worldwide is cigarette smoking. This also includes the smoking of pipes as pipe tobacco contains many of the same type of carcinogens as cigarette tobacco. 

Cancer risk increases with the time and number of cigarettes smoked. However, if a person quits smoking (even after smoking for many years), the chances of reducing the risk of developing lung cancer can be significant. Smoking cessation medications and counselling can be effective in helping you stay away from smoking in the long term. 

Active smoking is not the only way an individual may get lung cancer. Inhaling secondhand smoke, also known as involuntary or passive smoking, can pose a considerable risk. Therefore, stopping smoking will not only reduce the risk of lung cancer and improve the health of the smoker but that of household members as well.

Other risk factors associated with lung cancer include:

  • Family history of lung cancer.
  • Occupational exposure to substances such as asbestos, arsenic, chromium, beryllium, nickel, or tar.
  • Exposure to radiation from radiation therapy, radon, or imaging investigations, such as CT scans.
  • Air pollution


Types of lung cancers in smokers

Smoking has the potential to cause two particular types of lung cancer. They are:

  • Small cell lung cancer (SCLC): This type of cancer is uncommon and is usually found in individuals with a long history of tobacco smoking; Early diagnosis and management  has the potential to increase life expectancy.
  • Non-small cell lung cancer (NSCLC): This epithelial lung cancer accounts for more than 80% of lung cancers and can be classified into three subtypes – squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Squamous cell cancer is typically associated with long-term smoking.
What are the symptoms and signs of lung cancer?

The following symptoms and signs may be seen with lung cancer:

  • Headache
  • Chronic cough
  • Chest pain
  • Breathing difficulties
  • Hoarse voice
  • Blood in sputum (phlegm or mucus)
  • Loss of appetite
  • Unintended weight loss
  • Fatigue
  • Bone pain
  • Swelling of the face and neck veins

In the early stages of lung cancer, patients may be asymptomatic (no symptoms). Symptoms usually occur when the disease is advanced. As such, if you believe you are at risk or have symptoms that do not resolve on their own, it is advisable to see a lung specialist who will be able to conduct a thorough evaluation of your respiratory condition and advise on appropriate treatment if necessary.

How does smoking cause lung cancer?

The lung isn’t the only place affected by cigarette smoking. It can affect other parts of the body, such as the mouth, voice box, trachea, oesophagus, stomach, colon, rectum, liver, pancreas, and so on. It also significantly impacts an individual’s DNA or deoxyribonucleic acid (the hereditary component in humans). It can increase DNA methylation — a biological process that can change the activity of DNA segments and cause DNA damage. Smoking provides direct exposure of the epithelial tissue to at least 60-70 harmful carcinogens that may result in the damage of segments of DNA and thereby leading to lung cancer.

Some examples of such toxic carcinogens include:

  • Arsenic
  • Benzene
  • Cadmium
  • Formaldehyde
  • Nickel
  • Lead
  • Isoprene
How to diagnose and treat lung cancer?

The following investigations may be carried out to diagnose lung cancer:

  • Medical and family history.
  • Physical examination.
  • Imaging tests, such as chest X-ray or CT scan.
  • Lab investigations (including blood and sputum tests).
  • Lung biopsy.

Once the diagnosis is made, the specialist will classify the cancer according to the stages — this will offer integral information regarding the extent of cancer and the required response to the treatment. Screening for lung cancer is generally performed using a low-dose computerised tomography scan (LDCT). This scan doesn’t take up much time and isn’t painful.

How to prevent lung cancer?

Here are some strategies which can help prevent lung cancer:

  • Stop smoking.
  • Avoid secondhand smoke.
  • Reduce exposure to toxic chemicals such as asbestos, arsenic, radon, and lead.
Electronic cigarettes

While electronic cigarettes (e-cigarettes) appear less harmful than cigarettes, they are not safe. E-cigarettes (also known as vaping products) contain many harmful chemicals such as nicotine and heavy metals that can be inhaled deep into the lungs. The flavours in e-cigarettes are also known to be carcinogenic. Vaping comes with the risk of serious lung diseases like asthma, lung scarring, popcorn lung among others. It is generally believed that e-cigarettes don’t usually contain tobacco but this is not always the case; E-cigarettes often contain nicotine which comes from tobacco and is the key ingredient responsible for continued addiction. As such, e-cigarettes are classified as tobacco products by the Food & Drug Administration (FDA) in the U.S.

There are several harmful health effects linked with prolonged tobacco use. They include:

  • Heart disease
  • Stroke
  • Leukaemia
  • Type 2 Diabetes
  • Cataracts

Cigarette smoking is one of the major causes of illness and death in Singapore. According to statistics, over 90% of lung cancer cases are caused by smoking. Therefore, it is wise to consult a lung specialist if you need any assistance with quitting smoking.