Lung cancer is a type of cancer that develops when abnormal cells in the lungs grow uncontrollably and form a tumour. It is one of the leading causes of cancer-related deaths worldwide. Although smoking is the most common risk factor, lung cancer can also affect people who have never smoked. Recognising possible symptoms, understanding the risk factors, and seeking timely medical evaluation can help with early diagnosis and treatment. Treatment options include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy, depending on the type and stage of cancer.

What Is Lung Cancer?

Lung cancer occurs when cells in the lungs undergo changes that cause them to multiply abnormally. These cells may form a tumour, damage nearby lung tissue, and sometimes spread to other parts of the body through the blood or lymphatic system.

Lung cancer can affect one or both lungs. It may develop in the airways, lung tissue, or other structures within the lungs. Some people do not experience noticeable symptoms in the early stages, which can make diagnosis challenging.

What Are the Different Types of Lung Cancer?

Lung cancer is broadly classified into two main types based on how the cancer cells appear under a microscope.

1. Non-Small Cell Lung Cancer (NSCLC)

Non-small cell lung cancer is the most common type, accounting for approximately 85% of lung cancer cases. It generally grows and spreads more slowly than small cell lung cancer, although its behaviour varies depending on the subtype.

The main subtypes include:

• Adenocarcinoma: Usually develops in the outer areas of the lungs and is the most common type of lung cancer. It can occur in smokers as well as people who have never smoked.

• Squamous Cell Carcinoma: Often develops in the cells lining the airways and is strongly associated with tobacco smoking.

• Large Cell Carcinoma: A less common type that can develop in different parts of the lungs and may grow or spread quickly.

2. Small Cell Lung Cancer (SCLC)

Small cell lung cancer is less common but tends to grow and spread more rapidly than non-small cell lung cancer. It is strongly associated with smoking and is often diagnosed after it has spread beyond the lungs.

It is generally classified into two stages:

• Limited-stage disease: Cancer is present in a relatively restricted area of the chest and may be treated within a single radiation field.

• Extensive-stage disease: Cancer has spread beyond the limited area, including to distant organs.

What Are the Early Symptoms of Lung Cancer?

Lung cancer may not cause noticeable symptoms during its early stages. When symptoms appear, they can sometimes resemble common respiratory conditions. Persistent or unexplained changes in breathing or general health should not be ignored.

Common symptoms include:

• Persistent cough: A cough that lasts for several weeks, does not improve, or gradually becomes worse may be a warning sign.

• Coughing up blood: Blood in the sputum, even in small amounts, requires prompt medical evaluation.

• Chest pain: Pain or discomfort in the chest may become more noticeable while coughing, laughing, or taking a deep breath.

• Shortness of breath: Tumour growth or fluid accumulation around the lungs may make breathing difficult.

• Repeated chest infections: Frequent episodes of pneumonia or bronchitis, particularly in the same area of the lung, may need further investigation.

• Wheezing: A new or persistent whistling sound while breathing can occur when an airway becomes narrowed or blocked.

• Hoarse voice: Changes in the voice that do not improve may occur if a tumour affects nerves involved in voice production.

• Unexplained weight loss: Losing weight without changes in diet or physical activity can sometimes indicate an underlying illness.

• Persistent fatigue: Feeling unusually tired or weak despite adequate rest may occur with lung cancer.

• Loss of appetite: Reduced interest in food may accompany other symptoms and contribute to unintended weight loss.

What Are the Symptoms of Advanced Lung Cancer?

When lung cancer spreads to other parts of the body, it can cause additional symptoms depending on the affected organ.

• Bone pain: Cancer that spreads to the bones may cause persistent pain, particularly in the back, hips, or ribs.

• Headaches: Spread to the brain may cause recurring headaches or other neurological symptoms.

• Seizures: Brain involvement can sometimes lead to seizures or changes in consciousness.

• Weakness or numbness: Cancer affecting the brain or spinal cord may cause weakness, numbness, or difficulty with balance.

• Jaundice: If cancer spreads to the liver, the skin and whites of the eyes may become yellow.

• Swelling of the face or neck: A tumour may obstruct blood flow through a large vein in the chest, causing swelling in the face, neck, or upper body.

What Causes Lung Cancer?

Lung cancer develops because of changes in the DNA of lung cells that affect how they grow and divide. These changes may occur due to exposure to cancer-causing substances, lifestyle factors, environmental conditions, or a combination of influences.

The main risk factors include:

• Smoking tobacco: Cigarette smoking is the leading risk factor for lung cancer. Tobacco smoke contains harmful chemicals that can damage the DNA of lung cells.

• Secondhand smoke: Regular exposure to smoke from other people's cigarettes, cigars, or other tobacco products can increase lung cancer risk.

• Air pollution: Long-term exposure to polluted air, including fine particulate matter, can contribute to lung cancer risk.

• Occupational exposure: Working with substances such as asbestos, silica, diesel exhaust, and certain industrial chemicals can increase the risk.

• Radon exposure: Radon is a naturally occurring radioactive gas that can accumulate inside buildings and increase lung cancer risk when inhaled over time.

• Family history: Having a close relative with lung cancer may increase an individual's risk, although this does not mean the disease will necessarily develop.

• Previous radiation therapy: People who have received radiation treatment to the chest for another cancer may have an increased risk.

• Chronic lung diseases: Certain long-term lung conditions, including chronic obstructive pulmonary disease (COPD), are associated with a higher risk of lung cancer.

How Is Lung Cancer Diagnosed?

Lung cancer diagnosis involves identifying abnormal growths, confirming whether they are cancerous, determining the cancer type, and checking whether it has spread. Doctors may recommend several tests depending on the patient's symptoms and medical history.

Common diagnostic tests include:

• Physical examination and medical history: The doctor reviews symptoms, smoking history, occupational exposure, family history, and overall health.

• Chest X-ray: This imaging test can identify suspicious masses, abnormal shadows, or other changes in the lungs. However, a normal chest X-ray does not completely rule out lung cancer.

• CT scan: A computed tomography scan provides detailed images of the lungs and helps identify the size, location, and appearance of suspicious growths.

• PET-CT scan: This scan helps assess whether cancer may have spread to lymph nodes or other parts of the body.

• MRI scan: An MRI, particularly of the brain, may be recommended to check for cancer spread when clinically indicated.

• Sputum cytology: A sample of mucus coughed up from the lungs is examined under a microscope to look for abnormal cancer cells. This test is useful in selected cases but cannot detect every lung cancer.

• Bronchoscopy: A thin, flexible tube with a camera is passed through the nose or mouth into the airways. It allows the doctor to examine the lungs and collect tissue samples if necessary.

• Biopsy: A small sample of suspicious tissue is collected and examined under a microscope to confirm whether cancer is present and identify its type.

• Molecular testing: Tumour tissue may be tested for specific genetic changes and protein markers. These results can help doctors select targeted therapy or immunotherapy.

What Are the Stages of Lung Cancer?

Lung cancer staging describes how large the tumour is and whether it has spread to nearby lymph nodes or distant organs. It helps doctors plan treatment and understand the likely course of the disease.

Non-small cell lung cancer is generally classified into four main stages:

• Stage 1: Cancer is limited to the lung and has not spread to nearby lymph nodes. Surgery may be an option for eligible patients.

• Stage 2: Cancer may be larger or may have spread to nearby lymph nodes or structures within the chest. Treatment may involve surgery, chemotherapy, radiation therapy, or a combination.

• Stage 3: Cancer has spread to lymph nodes or nearby structures in the chest. Treatment often involves a combination of chemotherapy, radiation therapy, immunotherapy, or surgery in selected cases.

• Stage 4: Cancer has spread to distant organs or to areas beyond the original lung. Treatment generally focuses on controlling cancer growth, managing symptoms, and improving quality of life.

What Are the Treatment Options for Lung Cancer?

Lung cancer treatment depends on several factors, including the cancer type, stage, tumour location, genetic changes, and the patient's overall health. Doctors may recommend one treatment or a combination of therapies.

1. Surgery

Surgery may be recommended for certain patients with non-small cell lung cancer, particularly when the tumour is localised and can be removed safely.

Common surgical procedures include:

• Wedge resection: Removes a small, wedge-shaped portion of the lung containing the tumour along with a margin of healthy tissue.

• Segmentectomy: Removes one anatomical segment of the lung while preserving the remaining lung tissue.

• Lobectomy: Removes the affected lobe of the lung. It is a commonly performed operation for suitable patients with localised lung cancer.

• Pneumonectomy: Removes an entire lung when the tumour's location or extent makes a smaller operation unsuitable.

The choice of surgery depends on the tumour's size and location, lung function, and the patient's ability to tolerate the procedure.

2. Chemotherapy

Chemotherapy uses medicines to destroy cancer cells or stop them from multiplying. It may be used before surgery to shrink a tumour, after surgery to reduce the risk of recurrence, or as a main treatment for cancers that cannot be removed surgically.

• Before surgery: Chemotherapy may help reduce tumour size and improve the chances of successful treatment.

• After surgery: It may destroy remaining cancer cells and lower the risk of cancer returning.

• For advanced cancer: It may help control cancer growth, relieve symptoms, and improve quality of life.

Chemotherapy can cause side effects such as nausea, fatigue, hair loss, reduced blood cell counts, and an increased risk of infection. The side effects vary depending on the medicines used.

3. Radiation Therapy

Radiation therapy uses high-energy radiation to damage cancer cells and prevent them from growing. It may be used alone or in combination with other treatments.

• External beam radiation therapy: Radiation is delivered to the tumour from a machine outside the body.

• Stereotactic body radiation therapy (SBRT): Uses highly focused radiation doses to treat small, localised tumours, particularly when surgery is not suitable.

• Combined treatment: Radiation may be given with chemotherapy for certain locally advanced lung cancers.

• Symptom relief: Radiation may help reduce pain, bleeding, or breathing difficulties caused by cancer.

4. Targeted Therapy

Targeted therapy uses medicines that act on specific genetic changes or proteins that help cancer cells grow. It is mainly used when testing identifies a suitable target in the tumour.

• EGFR-targeted medicines: Used for certain lung cancers with specific EGFR gene changes.

• ALK-targeted medicines: Help treat cancers with ALK gene rearrangements.

• Other targeted treatments: Medicines may also be available for selected changes involving genes such as ROS1, BRAF, MET, RET, and KRAS.

These treatments are not suitable for every patient. Molecular testing helps determine whether a tumour has changes that can be treated with targeted medicines.

5. Immunotherapy

Immunotherapy helps the body's immune system recognise and attack cancer cells. It works by affecting specific immune pathways that cancer cells may use to avoid immune detection.

• Immune checkpoint inhibitors: These medicines target proteins such as PD-1, PD-L1, or CTLA-4 to help the immune system respond against cancer.

• Combination treatment: Immunotherapy may be used with chemotherapy or other treatments in selected patients.

• Advanced lung cancer: It may be recommended for certain patients with advanced non-small cell lung cancer and some cases of small cell lung cancer.

Immunotherapy can cause immune-related side effects, in which the immune system attacks healthy organs such as the lungs, liver, thyroid, or intestines. Regular monitoring is important during treatment.

6. Palliative and Supportive Care

Palliative care focuses on improving comfort and quality of life for people living with lung cancer. It can be provided alongside cancer treatment at different stages of the disease.

• Pain management: Medicines and other supportive measures help control cancer-related pain.

• Breathing support: Treatment may help manage breathlessness and other respiratory symptoms.

• Nutritional support: Dietitians can help patients manage appetite changes, weight loss, and treatment-related eating difficulties.

• Emotional support: Counselling and psychological care can help patients and families cope with the challenges of cancer.

• Symptom management: Supportive treatment can address fatigue, nausea, sleep problems, and other symptoms.

How Can Lung Cancer Be Prevented?

Not all cases of lung cancer can be prevented. However, reducing exposure to known risk factors can lower the risk of developing the disease.

• Avoid smoking: Not starting smoking is one of the most effective ways to reduce lung cancer risk.

• Quit tobacco: Stopping smoking at any age can improve overall health and gradually reduce the risk of lung cancer.

• Avoid secondhand smoke: Stay away from environments where people smoke and maintain smoke-free indoor spaces.

• Reduce workplace exposure: Follow safety guidelines when working with asbestos, silica, diesel exhaust, and other harmful substances.

• Check for radon exposure: Where radon is a concern, testing and appropriate measures can help reduce indoor exposure.

• Reduce air pollution exposure: Follow local air-quality guidance and limit exposure to heavily polluted environments when possible.

• Maintain a healthy lifestyle: Eat a balanced diet, stay physically active, and maintain a healthy weight to support overall health.

Who Should Consider Lung Cancer Screening?

Lung cancer screening is intended to detect cancer before symptoms develop in people who have a higher risk of the disease. It is not the same as diagnostic testing for someone who already has symptoms.

• Low-dose CT scan: This is the recommended screening test for eligible people at high risk of lung cancer.

• People with a significant smoking history: Screening recommendations generally consider age and the number of years and amount a person has smoked.

• Former smokers: People who have quit smoking may still qualify for screening depending on their age and smoking history.

• Individual risk assessment: A healthcare professional can help determine whether screening is appropriate based on personal risk factors and medical history.

Screening recommendations differ between countries and healthcare organisations. A chest X-ray or routine blood test is not a substitute for low-dose CT screening.

When Should You See a Doctor?

Certain symptoms should not be ignored, especially when they persist, worsen, or occur without an obvious explanation.

Seek medical evaluation if there is:

• A persistent cough: A cough lasting more than three weeks or one that gradually becomes worse.

• Blood in the sputum: Coughing up blood, even in small amounts, requires prompt assessment.

• Unexplained chest pain: Persistent chest discomfort, particularly when breathing or coughing.

• Breathing difficulties: New or worsening shortness of breath or wheezing.

• Repeated respiratory infections: Frequent episodes of pneumonia or bronchitis.

• Unexplained weight loss: Losing weight without changes in diet or activity.

• Persistent fatigue: Ongoing tiredness or weakness that affects daily activities.

Conclusion

Lung cancer can develop without obvious early symptoms, making awareness of warning signs and risk factors important. Smoking is the leading risk factor, but people who have never smoked can also develop the disease. Early medical evaluation, appropriate diagnostic tests, and personalised treatment can help improve outcomes. Treatment may involve surgery, chemotherapy, radiation therapy, targeted therapy, immunotherapy, or supportive care, depending on the type and stage of cancer.

FAQs

1. What are the first warning signs of lung cancer?

A persistent cough, coughing up blood, chest pain, shortness of breath, and unexplained weight loss can be early warning signs. Some people may not experience noticeable symptoms in the initial stages.

2. Can lung cancer develop in people who have never smoked?

Yes, lung cancer can occur in people who have never smoked. Factors such as secondhand smoke, air pollution, radon exposure, occupational hazards, and genetic changes may increase risk.

3. Is lung cancer curable?

Some lung cancers, particularly those diagnosed at an early stage, can be treated with the aim of achieving a cure. Treatment outcomes depend on the cancer type, stage, overall health, and response to treatment.

4. What is the best test to detect lung cancer early?

Low-dose CT scanning is recommended for lung cancer screening in eligible people who have a high risk of the disease. People with symptoms may need diagnostic tests such as a CT scan and biopsy.

5. What are the treatment options for advanced lung cancer?

Advanced lung cancer may be treated with chemotherapy, targeted therapy, immunotherapy, radiation therapy, or a combination of these treatments. Palliative care can also help manage symptoms and improve quality of life.