Lung Cancer

Lung cancer is one of the most commonly diagnosed cancers worldwide and remains a leading cause of cancer death, largely because it is so often found only after it has already spread. This is not because lung cancer is unusually aggressive compared to other cancers, but because the lungs have relatively few pain-sensing nerves and a great deal of reserve capacity — so a tumour can grow substantially before it causes symptoms noticeable enough to prompt a doctor's visit.

Lung cancer occurs when cells within the lung tissue — the paired organs in the chest that draw in oxygen with every breath and release carbon dioxide with every exhale — grow and divide abnormally. The great majority of cases are linked to long-term tobacco smoking, though lung cancer can also develop in people who have never smoked, driven by genetic factors, air pollution, or occupational exposures. Understanding a patient's individual risk profile is central to deciding whether proactive screening is appropriate, since screening is what allows lung cancer to be caught before symptoms appear.

What Is the Lung, and How Does Cancer Develop Here?

The lungs sit within the chest, protected by the ribcage, and are responsible for one of the body's most essential functions: exchanging oxygen from the air we breathe for carbon dioxide from the bloodstream. Air travels down the windpipe into branching airways that end in millions of tiny air sacs, where this gas exchange takes place across an enormous surface area.

Lung cancer develops when cells lining the airways or air sacs accumulate genetic damage that causes them to grow uncontrollably. In most cases, this damage accumulates over years of exposure to a carcinogen — overwhelmingly tobacco smoke, but also radon, asbestos, air pollution, or certain occupational chemicals. As the abnormal cells multiply, they can form a tumour that grows within the lung, invade nearby structures, or spread through the bloodstream or lymphatic system to other parts of the body.

Types of Lung Cancer

Lung cancer is broadly divided into two main categories, which behave differently and are treated differently.

Non-Small Cell Lung Cancer (NSCLC): The most common type, accounting for over 80% of cases. It includes adenocarcinoma, the most frequent subtype and the one most often seen in non-smokers, and squamous cell carcinoma, which is more strongly linked to smoking. NSCLC tends to grow and spread more slowly than small cell lung cancer, which generally means more treatment options are available, particularly when caught early.

Small Cell Lung Cancer (SCLC): A less common but more aggressive type that grows and spreads more quickly than NSCLC. It is frequently found only after it has already spread beyond the lung, and it responds differently to treatment, generally being more sensitive to chemotherapy and radiotherapy but with a higher tendency to recur.

Other Lung Tumors: Less common cancers that can also arise in or around the lung, including lymphomas, sarcomas, and pleural mesothelioma — a cancer of the lining of the lung strongly associated with asbestos exposure.

Stages of Lung Cancer

Lung cancer staging follows the TNM system, describing the size and extent of the primary Tumour, whether nearby lymph Nodes are involved, and whether the cancer has Metastasised to distant sites. These combine into an overall stage from I to IV, which is the single biggest factor guiding treatment choice and prognosis.

Stage 1

A small tumor confined to the lung, with no spread to lymph nodes.

Typical Approach: Potentially curative treatment: surgical removal, or stereotactic radiotherapy for patients unfit for surgery.

Stage 2-3

A larger tumor, or spread to nearby lymph nodes within the chest.

Typical Approach: A combination of surgery, radiotherapy, and chemotherapy or immunotherapy, tailored to the specific extent of disease.

Stage 4

Cancer has spread beyond the chest to distant organs, such as the brain, bone, or liver.

Typical Approach: Systemic therapy — targeted therapy, immunotherapy, and/or chemotherapy — aimed at controlling disease and preserving quality of life.

Because early-stage lung cancer so often causes no symptoms, roughly two in three cases are diagnosed only at stage III or IV, when the cancer has already spread. This gap between what screening can achieve and what typically happens without it is the strongest argument for proactive testing in anyone at meaningful risk.

Symptoms of Lung Cancer

Early lung cancer often causes no symptoms at all, and when symptoms do appear, they can easily be mistaken for less serious respiratory conditions, which is part of why diagnosis is so often delayed.

Early or non-specific symptoms

• A new or changed cough that does not go away
• Mild breathlessness, particularly on exertion
• Recurrent chest infections that do not fully clear
• Mild fatigue or reduced appetite

Symptoms of more advanced disease

• Persistent cough that worsens over time
• Coughing up blood or blood-streaked sputum
• Constant or worsening chest pain
• Shortness of breath that is new or progressively worsening
• Hoarseness of voice
• Difficulty swallowing
• Unexplained weight loss and appetite loss
• Wheezing

Symptoms requiring urgent assessment

• Coughing up significant amounts of blood
• Sudden or severe shortness of breath
• Severe, unexplained chest pain
• New neurological symptoms, such as headache, weakness, or confusion, which can indicate spread to the brain

Risk Factors for Lung Cancer?

Several factors influence lung cancer risk, and while smoking remains by far the most significant, a meaningful proportion of cases occur in people who have never smoked.

Underlying and non-modifiable risk factors

• Age, your risk rises significantly after age 50
• Family history of lung cancer
• Personal history of radiation therapy to the chest
• Certain genetic mutations, more commonly seen in non-smokers with lung cancer

Modifiable risk factors

• Cigarette smoking is linked to approximately 80–90% of lung cancer cases, with risk rising with both duration and intensity of smoking
• Exposure to second-hand smoke
• Exposure to air pollutants, including fine particulate matter
• Occupational exposure to asbestos, radon, diesel exhaust, or certain industrial chemicals

How Lung Cancer is Diagnosed

Diagnosis combines imaging, tissue sampling, and increasingly, molecular testing to guide treatment selection. A suspicious finding on a scan is not, by itself, a diagnosis — confirmation almost always requires a tissue sample.

• Low-Dose CT Scan: The standard screening test for high-risk individuals, and often the first imaging test to detect an abnormality, whether found through screening or in the course of investigating symptoms.
• CT Scan with Contrast: A more detailed diagnostic scan used to characterise a suspicious lung finding, assess its size and location, and check for spread to lymph nodes or other organs.
• PET-CT Scan: Combines CT imaging with a radioactive tracer that highlights areas of high metabolic activity, helping to determine the full extent of disease, including spread outside the chest.
• Biopsy: A tissue sample is taken, often guided by CT, bronchoscopy, or ultrasound, and examined under the microscope to confirm the diagnosis and identify the specific cancer type.
• Molecular & Biomarker Testing: Tumor tissue is tested for specific genetic mutations and protein markers. Results directly determine whether targeted therapy or immunotherapy is likely to be effective for that individual patient.
• Blood Tests: Used to assess overall health and organ function ahead of treatment planning, and in some cases to look for markers associated with cancer or its effects on the body.

Living with Lung Cancer and Reducing Your Risk

Whether newly diagnosed or managing lung cancer over the longer term, a number of everyday factors influence both treatment outcomes and overall wellbeing.

• Stop smoking — quitting improves treatment outcomes and reduces complications at any stage of diagnosis or treatment
• Attend all scheduled scans and follow-up appointments, even between active treatment cycles
• Discuss breathlessness or fatigue with your care team — pulmonary rehabilitation and supportive therapies can meaningfully improve daily function
• Maintain adequate nutrition, particularly during chemotherapy or radiotherapy, when appetite is often affected
• Reduce exposure to air pollution and second-hand smoke where possible
• Report new or worsening symptoms promptly rather than waiting for the next scheduled review
• Consider genetic counselling if there is a strong family history of lung cancer, particularly in non-smokers