Lung Cancer: Symptoms & Causes

According to the Singapore Cancer Registry (2018-2022), 9,012 lung cancer cases were diagnosed over 5 years, accounting for 13.7% of all male cancers and 7.7% of female cancers. It is also the leading cause of cancer deaths in men and the second in women, largely due to smoking causing lung cancer, but also impacting non-smokers via secondhand smoke and genetic mutations (e.g. EGFR, which are found in up to 60% of never-smoking Asian patients).

Late-appearing symptoms such as a persistent cough, chest pain, and shortness of breath underscore the importance of early screening. Lung cancer treatment involves specialised multidisciplinary clinics that guide the use of targeted therapies, immunotherapy, surgery, and radiation therapy.

At Neumark, we understand these patterns. Our lung cancer screening in Singapore and treatment strategies go beyond traditional risk profiles to include younger patients, non-smokers, and those with a family history or genetic predisposition to developing lung cancer.

Lung Cancer Symptoms

Early lung cancer is often asymptomatic, presenting with no symptoms, making detection difficult until the disease has advanced. Initial symptoms of lung cancer, such as coughs, difficulty swallowing, coughing up blood, a chronic cough that doesn’t go away, chest pain, and shortness of breath, are often mistaken for other conditions.
  

Complications

In more advanced stages, lung cancer may present with additional advanced lung cancer symptoms such as:

• Pleural effusion (fluid buildup around the lungs)
• Severe fatigue
• Bone pain if the cancer spreads to the bones
• Neurological symptoms, if there’s brain involvement with other organs
• Unexplained weight loss
• Hoarseness or difficulty swallowing
• Trouble breathing 

When to See a Doctor

See your doctor in Singapore if you have any lung cancer symptoms. If you smoke and struggle to quit, see your healthcare professional for quitting smoking strategies, including counselling, medicines and nicotine replacement.

Please note that the presence of these first symptoms of lung cancer doesn’t mean lung cancer, but they do warrant medical attention. Early detection can impact lung cancer treatment options and outcomes. If you have persistent respiratory symptoms or unexplained changes in your health, it’s best to consult a lung cancer specialist in Singapore, like Neumark, for a thorough evaluation to see if you have early symptoms of lung cancer.

What Causes Lung Cancer?

Lung cancer causes include changes in the DNA of lung or airway cells, which act as an instruction manual for the cell. In healthy cells, those instructions keep growth under control and prompt old or damaged cells to die at the right time. When cancer-related changes occur, the signals become distorted. Abnormal cells multiply too quickly and can survive longer than they should, leading to a buildup of cancer cells.

Over time, these cancer cells may form a tumour. As it enlarges, it can invade nearby lung tissue, interfere with normal lung function, and damage lung tissue. Cancer cells can also break away and travel to other parts of the body via the bloodstream or lymphatic system. When this happens, the cancer spreads, and it is called metastatic lung cancer.

Smoking remains the main cause of lung cancer, and secondhand smoke exposure also increases the risk of lung cancer. However, lung cancer can develop even in people who have never smoked, and in these cases, the causes of lung cancer in nonsmokers are not always clear. Other risk factors that can raise risk include exposure to asbestos or radon gas, certain workplace or environmental toxins, chronic lung disease such as COPD, and a family history of lung cancer.

In Singapore, doctors are seeing more lung cancer in never-smokers as well, which is why symptoms of lung cancer, imaging test findings, and lung cancer screening guidelines eligibility deserve careful attention, even if you have never touched a cigarette.  
 

How Smoking Causes Lung Cancer

Smoking can cause lung cancer by damaging the lung cells that line the lungs. Cigarette smoking contains many cancer-causing substances, called carcinogens. When these cancer-causing substances enter the lungs, they can damage a cell’s DNA and change the instructions that tell the cell how to behave.

At first, the immune system and body can repair some of this damage. But cigarette smoking exposes the lungs to carcinogens again and again. Each exposure can lead to additional DNA changes. Over time, the damage builds up. The cells may begin to grow and multiply uncontrollably and may not die when they should. This can lead to the abnormal growth and formation of a tumour and, eventually, lung cancer.

Types of Lung Cancer

There are two main types of lung cancer, each with distinct characteristics and prevalence rates.  
 

Small Cell Lung Cancer (SCLC)

An aggressive, fast-growing type of lung cancer in which the cells are small and oval under a microscope. Small-cell lung cancer is most strongly linked to smoking heavily over the years and tends to spread (metastasise) to parts of the body. In small-cell lung cancer, two stages are identified: limited and extensive, based on the extent of cancer spread. It is less common than non-small cell lung cancer.  
 

Non-Small Cell Lung Cancer (NSCLC)

The most common lung cancer type accounts for about 85% of all lung cancer. Non-small cell lung cancer is defined as any epithelial lung cancer other than small cell lung cancer, characterised by larger cells that grow more slowly than small cell lung cancer. Non-small cell lung cancer includes subtypes such as:

• Adenocarcinoma: Begins in cells that make mucus and other substances in the lungs. It often starts in the outer parts of the lung.
• Squamous cell carcinoma: Starts in squamous cells. These are flat cells that line the airways in the lungs. This type often develops in the larger breathing tubes near the centre of the chest cavity.
• Large cell carcinoma: A group of lung cancers where the cells look large and abnormal under a microscope, but they do not fit neatly into the adenocarcinoma or squamous categories. It can start in different parts of the lung.

Risk Factors

A number of risk factors can increase the risk of developing lung cancer. Some risk factors can be controlled, such as smoking. Others cannot be controlled, such as your age or family history. Having one risk factor does not mean you will get lung cancer. Some develop lung cancer without any clear risk factors.

Risk factors for lung cancer include:  
 

Smoking

Smoking is the biggest risk factor for lung cancer. Your risk rises with how many cigarettes you smoke each day and how many years you have smoked. Quitting helps at any age. The longer you stay smoke-free, the lower your risk of lung cancer falls over time.  
 

Exposure to Second-Hand Smoke

You do not have to smoke to be affected. Breathing in secondhand smoke from other people’s cigarettes, cigars or pipes is called secondhand smoke. Regular exposure increases lung cancer risk.  
 

Previous Radiation Therapy to the Chest

Radiation therapy to the chest for another cancer can increase the risk of developing lung cancer later in life. The risk may be higher if you also smoke.  
 

Exposure to Radon Gas

Radon is a naturally occurring radioactive gas that forms from the decay of uranium in soil and rock. It can build up indoors, including in homes and buildings. Breathing in radon gas over time increases lung cancer risk.  
 

Exposure to Cancer-Causing Substances at Work

Some workplaces expose people to substances that can damage lung cells over time. These substances are called carcinogens. Examples include asbestos, arsenic, chromium, nickel, diesel exhaust and certain industrial chemicals. The risk is higher when these exposures happen together with smoking.  
 

Family History of Lung Cancer

If a parent, sibling, or child has had lung cancer, your risk is higher. This may be linked to shared genes, shared environments, or both.  
 

Air Pollution

Long-term exposure to high levels of air pollution can increase the risk of lung cancer. This includes outdoor air pollution and indoor pollution from fumes or smoke.  
 

Chronic Lung Disease

Certain long-term lung conditions can raise risk, especially when combined with smoking. These include chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis. Long-term inflammation and scarring in the lungs may be contributing factors.  
 

Exposure to Asbestos and Other Fibres

Asbestos exposure is a well-known risk factor. It can also lead to conditions such as asbestosis and mesothelioma. The combination of asbestos exposure and smoking increases lung cancer risk more than either factor alone.  
 

Smoking Other Substances

Regular exposure to smoke from other sources, such as heavy cannabis smoking, may increase risk, though the data is less clear than for cigarette smoking. Any inhaled smoke contains irritants and chemicals that can damage lung tissue.  
 

Weakened Immune System and Certain Medications

People with reduced immune system function, including those on long-term immunosuppressant medicines after an organ transplant, may have a higher risk of some cancers, including lung cancer.  
 

Age

Risk increases with age. Lung cancer is more common in older adults because DNA damage builds up over time.

If you are worried about your risk, the next step is not to panic. It is a calm assessment of your exposures, symptoms, and whether you might benefit from screening or further testing.

Prevention

There is no sure way to prevent lung cancer. However, there are steps you can take to lower your risk. Some steps reduce exposure to things that damage lung cells. Others help your body stay as healthy as possible if you do develop a problem. Prevention is not about perfection. It is about reducing risk over time.  
 

Do Not Smoke

If you have never smoked, do not start. Smoking is the biggest preventable cause of lung cancer. If you have children or teenagers at home, start conversations early. Explain that smoking is not just a habit. It exposes the lungs to chemicals that can damage DNA and lead to cancer.  
 

Stop Smoking

If you smoke, quitting smoking is the single most important step you can take. Quitting lowers your risk of lung cancer even if you have smoked for years. Many need more than willpower. Nicotine replacement, prescription medicines, counselling and support groups can all help. Ask your healthcare team to guide you towards a plan that fits you.  
 

Avoid Second-Hand Smoke

Breathing smoke from others’ cigarettes also raises lung cancer risk. If someone in your home smokes, encourage them to quit. If that is not possible, ask them to smoke outside and away from windows and doors. Choose smoke-free places whenever you can.  
 

Reduce Exposure to Radon

Radon is a naturally occurring gas that can accumulate indoors. Breathing it over long periods increases risk. If radon is a concern where you live, testing your home is a practical step. If levels are high, ventilation and remediation can reduce exposure.  
 

Protect Yourself from Workplace Carcinogens

Some jobs involve exposure to substances that can damage the lungs over time, such as asbestos, silica dust, diesel exhaust, and certain metals and chemicals. Follow workplace safety rules. Use protective equipment properly. If you are unsure about your exposure risk, ask for an occupational health assessment. Smoking lung cancer increases the harm caused by many workplace carcinogens, so quitting matters even more.  
 

Reduce Exposure to Air Pollution and Indoor Fumes

Air pollution can increase lung cancer risk, especially with long-term exposure. You cannot control outdoor air quality at all times, but you can reduce indoor exposures. Avoid burning incense or using charcoal indoors. Use good ventilation when cooking. Limit exposure to strong chemical fumes and consider a well-fitted mask if you work in dusty environments.
   

Treat and Manage Chronic Lung Disease

Conditions such as chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis are linked with a higher risk of lung cancer. Managing these conditions well and avoiding smoking can help protect lung health. If you have a chronic lung condition, ask your doctor whether you need closer monitoring.  
 

Eat Well, But Be Cautious with Supplements

A diet rich in fruits and vegetables supports overall health. Food sources of vitamins and nutrients are best. Large doses of vitamin supplements are not a substitute for a healthy diet and can sometimes be harmful, especially in smokers. If you are considering supplements, speak to your doctor first.  
 

Stay Physically Active

Regular exercise supports lung and heart health and helps with weight control, mood, and sleep. If you do not exercise now, start small. A brisk walk most days is a good beginning. Consistency matters more than intensity.  
 

Know Your Eligibility for Screening

For some patients at higher risk, screening with a low-dose CT scan can find early-stage lung cancer earlier, sometimes before symptoms start in early stages. Screening is not for everyone. It is most helpful in specific age and smoking-history groups based on lung cancer screening guidelines. If you are unsure, ask a doctor to assess your risk and discuss whether screening is appropriate. 
 

Pay Attention to Persistent Symptoms

Prevention also includes not ignoring warning signs and symptoms of lung cancer. A persistent cough, coughing up blood, ongoing breathlessness, unexplained weight loss, or chest pain that does not settle deserves medical review, especially if you have risk factors. Early evaluation does not mean you have cancer. It means you are taking your health seriously.