17. Lung cancer

Lung cancer

Lung cancer is a leading cause of cancer mortality. Cigarette smoking is the dominant risk factor; others include radon, asbestos, silica, air pollution, prior thoracic irradiation and family history.
Major groups are non-small-cell lung cancer (NSCLC: adenocarcinoma, squamous-cell carcinoma and large-cell/other types) and small-cell lung cancer (SCLC).
Adenocarcinoma is common in peripheral lung and occurs in smokers and non-smokers. Squamous carcinoma is associated strongly with smoking and often arises centrally. SCLC is an aggressive neuroendocrine tumour with early dissemination.
Paraneoplastic syndromes include SIADH and ectopic ACTH in SCLC, hypercalcaemia in squamous carcinoma, and hypertrophic pulmonary osteoarthropathy.

Carcinogenesis involves accumulated genetic and epigenetic alterations; molecular drivers such as EGFR, ALK, ROS1, BRAF, MET, RET, NTRK and KRAS can guide targeted therapy in selected NSCLC.
Spread occurs by direct invasion, hilar/mediastinal lymphatics and haematogenous metastasis, commonly to brain, bone, liver and adrenal glands.
Central tumours may obstruct bronchi, causing collapse, post-obstructive pneumonia or haemoptysis; apical (Pancoast) tumours may invade the brachial plexus and sympathetic chain.

Symptoms include persistent or changing cough, haemoptysis, dyspnoea, chest pain, recurrent pneumonia, hoarseness, weight loss, anorexia and fatigue.
Advanced disease may cause superior vena cava obstruction, dysphagia, bone pain, neurological symptoms, pleural effusion or Pancoast syndrome.
Examination may reveal clubbing, supraclavicular nodes, unilateral wheeze, collapse, pleural effusion, hepatomegaly or signs of metastasis.

Chest radiograph may identify a mass, collapse, effusion or hilar enlargement, but a normal radiograph does not exclude cancer.
Contrast-enhanced CT chest and upper abdomen defines the primary lesion, nodes and adrenal/liver lesions. PET-CT helps assess nodal and distant disease in potentially curable patients.
Tissue diagnosis is obtained by bronchoscopy/EBUS for central lesions and mediastinal nodes, CT-guided biopsy for peripheral lesions, or sampling of an accessible metastasis/effusion.
Histology, immunohistochemistry and molecular testing are essential. Brain MRI is used when indicated by stage, symptoms or treatment plan.
Stage NSCLC with TNM; SCLC is often described as limited-stage or extensive-stage for treatment planning. Assess performance status, lung function and cardiopulmonary fitness before curative treatment.

Management is multidisciplinary and depends on histology, stage, molecular profile, performance status and patient preference.
Early-stage NSCLC may be treated with anatomical resection and nodal assessment; stereotactic body radiotherapy is an option for selected medically inoperable patients.