Lung Cancer

Lung cancer, or lung carcinoma, is a malignant tumour originating in the lung tissue, often triggered by genetic damage to airway cells.

Tobacco smoking is the primary cause, but asbestos, radon, and other environmental mutagens also contribute. Early detection is difficult as initial symptoms are often absent or nonspecific.

Signs and Symptoms

Early lung cancer typically presents no symptoms. When symptoms arise, they are usually respiratory, including coughing, shortness of breath, and chest pain. Coughing may bring up blood, while shortness of breath and persistent chest pain are common. Systemic symptoms like loss of appetite, weight loss, and fever can also occur.

Specific tumour locations can cause additional symptoms, such as difficulty swallowing, hoarseness, and Horner's syndrome. Around one-third of patients experience symptoms from metastases, including headaches, bone pain, and liver enlargement. Paraneoplastic syndromes, due to hormone release, can cause hypercalcaemia, hypokalaemia, and hyponatraemia, among other complications.

Diagnosis

CT scan showing a cancerous tumour in the left lung

Imaging tests like chest X-rays and CT scans are initial steps in diagnosing suspected lung cancer. A definitive diagnosis requires a biopsy, often obtained via bronchoscopy or fine needle aspiration.

Histological examination by a pathologist confirms cancer and classifies it into small-cell lung cancer (SCLC) or non-small-cell lung cancer (NSCLC). NSCLC is further divided into adenocarcinoma, squamous-cell carcinoma, and large-cell carcinoma.

Staging assesses the cancer's spread and informs treatment. SCLC is staged as limited or extensive, while NSCLC uses the TNM system (Tumour, Node, Metastasis) to classify stages I-IV.

Treatment

Treatment varies based on cancer type, stage, and patient health. Early-stage NSCLC is often treated surgically, removing the tumour and possibly combining this with chemotherapy and radiotherapy. Advanced stages might use targeted molecular therapies and immune checkpoint inhibitors.

For SCLC, chemotherapy combined with radiotherapy is standard, though relapse is common. Limited-stage SCLC may benefit from prophylactic cranial irradiation to prevent brain metastases.

Setup for radiation therapy. The person lies flat while a radiation beam is focused on the tumour site.

The extent of common surgeries to remove a lung tumour (shown in black). Areas that are surgically removed along with the tumour are shown in blue.

Palliative care aims to improve quality of life by managing symptoms like pain and shortness of breath. Techniques include supplemental oxygen, stenting of obstructed airways, and pain management using the WHO three-tiered system. End-of-life care focuses on comfort, managing pain and respiratory distress, and addressing terminal secretions.

Brachytherapy (internal radiotherapy) for lung cancer given via the airway

Prognosis

Prognosis depends on cancer type, stage at diagnosis, and patient demographics. Five-year survival rates are around 19%, higher for early-stage diagnoses. SCLC has a poorer prognosis, with a five-year survival of 10-15%. Younger patients and those who quit smoking have better outcomes.

Lung cancer is the most diagnosed cancer globally, with 2.2 million cases in 2020. Incidence and survival rates vary widely, influenced by smoking prevalence and healthcare quality.

Percent of people who survive five years from a lung cancer diagnosis over time, according to the NIH SEER programme

Causes

Lung cancer primarily results from genetic mutations induced by tobacco smoke. Other significant causes include environmental exposures to asbestos, radon, and various industrial chemicals. Chronic inflammatory diseases of the lungs and genetic predispositions also contribute.

Relationship between cigarette consumption per person (blue) and male lung cancer rates (dark yellow) in the US

Prevention

Reducing lung cancer risk focuses on smoking cessation, bolstered by public health policies such as increased tobacco taxes, smoking bans, and public education. Dietary factors, body weight, and physical activity also influence risk. High consumption of fruits and vegetables and maintaining a healthy weight are associated with lower lung cancer risk.

No smoking sign at a train station in Colorado

Graphic cigarette packaging in Belgium labelled "open wound following lung surgery"

Epidemiology

Lung cancer is the most diagnosed and deadliest cancer worldwide, with significant geographic and gender variations. Tobacco smoking is the main risk factor, with secondhand smoke also contributing substantially. The incidence of lung cancer among non-smokers is stable or increasing even as overall rates decline due to reduced smoking prevalence.

Self-assessment MCQs (single best answer)

What is the primary cause of lung cancer?

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Which of the following is a systemic symptom of lung cancer?

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What is the main diagnostic method to confirm lung cancer?

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Which type of lung cancer is more likely to be treated with chemotherapy and radiotherapy rather than surgery?

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What is the five-year survival rate for early-stage lung cancer diagnosis?

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Which of the following is a common symptom of metastases in lung cancer patients?

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What staging system is used for non-small-cell lung cancer (NSCLC)?

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Which of the following is a preventive measure for reducing lung cancer risk?

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Paraneoplastic syndromes in lung cancer patients can cause all of the following EXCEPT:

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Which treatment aims to improve the quality of life by managing symptoms in lung cancer patients?

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