Lung cancer

Definition | Classification | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Lung cancer is a malignant tumour originating in the lung tissues, often associated with smoking and environmental exposures. It is one of the leading causes of cancer-related mortality worldwide.

Classification

Lung cancer is classified into two main types:

  • Non-Small Cell Lung Cancer (NSCLC): accounts for approximately 85% of lung cancers and includes:
    • Adenocarcinoma: this is the most common type, often found in non-smokers.
    • Squamous Cell Carcinoma: it's linked to smoking, usually central in location.
    • Large Cell Carcinoma: an aggressive and less common.
  • Small Cell Lung Cancer (SCLC): it accounts for 15% of cases, highly aggressive and strongly associated with smoking.

Aetiology

The main causes of lung cancer include:

  • Smoking: the main risk factor, responsible for the majority of cases.
  • Passive smoking: exposure to second hand smoking increases the risk.
  • Occupational exposure: asbestos, radon gas, arsenic, and other carcinogens.
  • Genetic predisposition: a family history increases susceptibility.
  • Air pollution: long-term exposure to pollutants like diesel exhaust fumes.

Pathophysiology

Lung cancer develops due to genetic mutations in lung epithelial cells:

  • Carcinogens (e.g., tobacco smoke) cause DNA mutations, leading to uncontrolled cell growth.
  • Loss of tumour suppressor genes (e.g., TP53) allows unchecked proliferation.
  • Invasion of local structures and distant metastasis via blood and lymphatic spread.

Risk factors

  • Smoking (active and passive exposure).
  • Occupational exposure to carcinogens.
  • History of chronic lung disease (e.g., COPD, pulmonary fibrosis).
  • Previous history of cancer or radiation therapy to the chest.
  • Age over 50 years.

Signs and symptoms

Local Symptoms:

  • Persistent cough lasting more than 3 weeks.
  • Haemoptysis (coughing up blood).
  • Dyspnoea (shortness of breath).
  • Chest pain or discomfort.
  • Hoarseness due to recurrent laryngeal nerve involvement.

Systemic Symptoms:

  • Unintentional weight loss.
  • Fatigue.
  • Loss of appetite.

Signs of Metastases:

  • Bone pain (bone metastases).
  • Neurological symptoms (brain metastases).
  • Liver dysfunction (liver metastases).

Investigations

  • Chest X-ray:
    • May show a lung mass, collapse, or pleural effusion.
  • CT Thorax: used for detecting tumour size, lymph node involvement, and metastases.
  • Bronchoscopy with Biopsy: for histological confirmation if the tumour is central.
  • PET-CT Scan: used for staging and assessing metastases.
  • Sputum Cytology: useful in centrally located tumours.
  • Blood Tests:
    • Full blood count (FBC) for anaemia or leukocytosis.
    • Liver function tests (LFTs) if metastases are suspected.

Management

  • NSCLC: surgical resection, chemotherapy, radiotherapy, targeted therapy, immunotherapy.
  • SCLC: chemotherapy, radiotherapy, immunotherapy.
  • Supportive Care: smoking cessation, palliative care, symptom management.

Referral

Refer to secondary care in the following scenarios:

  • Respiratory Specialist: for suspected lung cancer requiring imaging and biopsy.
  • Oncology Specialist: for staging and treatment planning.
  • Palliative Care Team: for symptom management in advanced disease.
  • Hospital admission:
    • Severe respiratory compromise requiring oxygen support.
    • Acute complications such as massive haemoptysis or superior vena cava obstruction.
 
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