Overview

Lung cancer is a malignant tumour arising from cells within the lungs or bronchi. Two main groups:

• Non-small cell lung cancer (NSCLC): approximately 85%
  • Adenocarcinoma
  • Squamous cell carcinoma
  • Large-cell carcinoma
• Small cell lung cancer (SCLC): approximately 15%
  • More aggressive, with early nodal and distant metastasis.

Lung cancer is the leading cause of cancer death worldwide. Globally in 2022:

• Approximately 2.5 million new cases
• Approximately 1.8 million deaths

Incidence rises markedly with age. Tobacco smoking is the major risk factor, but lung cancer can occur in people who have never smoked.

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Aetiology & Risk Factors

There are many risk factors for lung cancer. Smoking is the most common.

Other risk factors:

• Passive smoking
• Radon
• Asbestos, silica and diesel exhaust
• Air pollution
• Previous thoracic radiotherapy
• Chronic lung disease
• Genetic susceptibility and family history.

Lung Carcinoma Classification

Small cell lung carcinoma (SCLC – 20%)

Non-small cell lung carcinoma ( NSCLC – 80%)

• Adenocarcinoma
• Squamous cell carcinoma
• Large cell

Clinical Manifestations

Respiratory symptoms

• Persistent new or changing cough
• Dyspnoea
• Haemoptysis
• Chest or shoulder pain
• Wheeze
• Recurrent or non-resolving pneumonia
• Hoarse voice
• Reduced exercise tolerance

Constitutional symptoms

• Unintentional weight loss
• Anorexia
• Fatigue and weakness
• Fever or night sweats

Early lung cancer is frequently asymptomatic and may be detected incidentally on imaging.

Local invasion or compression

• Recurrent laryngeal nerve involvement: hoarseness
• Phrenic nerve involvement: diaphragmatic paralysis
• Oesophageal compression: dysphagia
• Superior vena cava obstruction: facial/neck swelling, distended chest veins and dyspnoea
• Pancoast tumour: shoulder or arm pain, brachial plexopathy
• Horner syndrome: ptosis, miosis and anhidrosis
• Pleural or pericardial effusion
• Airway obstruction causing collapse or post-obstructive pneumonia.

Metastatic manifestations

Common metastatic sites include the brain, bone, liver, adrenal glands and contralateral lung.

• Brain: headache, seizures, focal neurological deficits or personality change
• Bone: pain, pathological fracture or spinal cord compression
• Liver: hepatomegaly, abdominal discomfort or jaundice
• Adrenal metastases are often asymptomatic.

Paraneoplastic syndromes

• Small cell lung cancer:
  • SIADH → hyponatraemia
  • Ectopic ACTH → Cushing syndrome
  • Lambert–Eaton myasthenic syndrome
  • Paraneoplastic cerebellar degeneration
• Squamous cell carcinoma:
  • PTH-related peptide secretion → hypercalcaemia
• Digital clubbing and hypertrophic pulmonary osteoarthropathy may occur, particularly with NSCLC.

Diagnosis

Investigations

General

• Chest X-Ray – opacity
• Spirometry – if thinking of obstructive or restrictive lung disease
• CT

Investigations for staging

• CT- Biopsy
• PET scan
• Pleural fluid aspiration
• Lung biopsy with bronchoscopy
• Endobronchial ultrasound
• Sputum MCS

Treatment

Once a patient presents with symptoms or radiographic findings suggestive of lung cancer, the next steps are as follows:

1. Tissue diagnosis to establish malignant diagnosis and histologic type
2. Staging to determine resectability or curative potential
3. Cancer treatment: surgery, radiotherapy, or chemotherapy

Non-small cell lung cancer

Early-stage disease: stages I–II

• Surgical resection:
  • Lobectomy
  • Segmentectomy or wedge resection
• Stereotactic body radiotherapy—SBRT/SABR if medically inoperable
• +/- Neoadjuvant or adjuvant platinum-based chemotherapy
• Selected patients may receive perioperative or adjuvant:
  • Immunotherapy
  • EGFR-targeted therapy
  • ALK-targeted therapy
    depending on stage and tumour biomarkers.

Locally advanced disease: stage III

• Requires multidisciplinary assessment.
• Resectable disease: neoadjuvant chemotherapy ± immunotherapy followed by surgery in selected patients.
• Unresectable disease: concurrent platinum-based chemoradiotherapy.
• Consolidation immunotherapy, commonly durvalumab, may follow chemoradiotherapy when there has been no progression and the patient is eligible.

Metastatic disease: stage IV

• Usually treated with systemic therapy rather than curative surgery.
• Perform broad molecular profiling and PD-L1 testing.
• Actionable alterations may include:
  • EGFR
  • ALK
  • ROS1
  • BRAF V600E
  • KRAS G12C
  • MET exon 14
  • RET
  • NTRK
  • HER2
• Treatment options:
  • Targeted tyrosine-kinase therapy for an actionable driver
  • Immune-checkpoint inhibitor alone in selected patients
  • Immunotherapy plus platinum-based chemotherapy
  • Chemotherapy when immunotherapy or targeted treatment is unsuitable
• Palliative radiotherapy may treat painful bone disease, brain metastases, haemoptysis, airway obstruction or superior vena cava syndrome.
• Early supportive and palliative care should accompany anticancer treatment.

Small cell lung cancer

Limited-stage SCLC

• Concurrent platinum–etoposide chemotherapy and thoracic radiotherapy
• Surgery is rarely used and is generally limited to very early, node-negative disease.
• Selected responders may receive:
  • Consolidation immunotherapy according to local approval
  • Prophylactic cranial irradiation or MRI brain surveillance.

Extensive-stage SCLC

• Platinum–etoposide chemotherapy plus:
  • Atezolizumab, or
  • Durvalumab
• Radiotherapy for selected thoracic disease, brain metastases, bone pain or other symptoms.
• Recurrent disease options include topotecan, lurbinectedin, tarlatamab or other systemic therapies, depending on availability and previous response.

Complications & Prognosis

Complication

NSCLC

• Post-obstructive pneumonia/hypoxia
• Superior vena vaca syndrome
• Paraneoplastic syndromes

SCLC

• Post-obstructive pneumonia/hypoxia
• Superior vena vaca syndrome
• Paraneoplastic syndromes
• Chemothreapy induced hematological toxicity
• Radiation induced esophageal/lung injury

Prognosis

• Early-stage NSCLC may be potentially cured with surgery or definitive radiotherapy.
• SCLC often responds initially to chemotherapy but has a high rate of relapse.
• Prognosis is considerably poorer once distant metastases are present.
• Australian overall five-year relative survival was 27.3% for patients diagnosed during 2017–2021, improving from 9.5% during 1987–1991.
• US population data report approximate five-year survival of:
  • Localised: 65.5%
  • Regional: 38.2%
  • Distant metastatic: 10.5%

References 

1. World Health Organization. Lung cancer [Internet]. Geneva: World Health Organization; 2026.
2. Cancer Australia. Lung cancer in Australia statistics [Internet]. Canberra: Australian Government; 2026.
3. Cancer Australia. Types, risk factors and symptoms of lung cancer [Internet]. Canberra: Australian Government; 2026.
4. National Cancer Institute. Non-small cell lung cancer treatment (PDQ): health professional version [Internet]. Bethesda: National Cancer Institute; 2025.
5. National Cancer Institute. Small cell lung cancer treatment (PDQ): health professional version [Internet]. Bethesda: National Cancer Institute; 2025.