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Lung Cancer and Its Paraneoplastic Syndromes: A PLAB 2 Revision Guide

Introduction

Lung cancer is a common condition tested in PLAB 2. Beyond respiratory symptoms, it presents with paraneoplastic syndromes, systemic manifestations caused by hormones or immune responses produced by the tumour. This blog summarises key features for your exam preparation.


1. Symptoms from the Primary Tumour


✅ Respiratory Symptoms

  • Persistent cough (changing or worsening)

  • Haemoptysis (coughing up blood)

  • Shortness of breath

  • Chest pain (pleuritic or dull ache)

  • Wheezing


✅ Constitutional Symptoms

  • Unexplained weight loss

  • Fatigue and weakness

  • Loss of appetite


✅ Local Invasion Symptoms

  • Hoarseness (recurrent laryngeal nerve palsy)

  • Difficulty swallowing (dysphagia)

  • Superior vena cava (SVC) obstruction – facial swelling, distended neck veins

  • Horner’s syndrome (ptosis, miosis, anhidrosis) from Pancoast tumour invading sympathetic chain


2. Metastasis Routes and Symptoms


✅ Common Sites of Metastasis

  • Brain: Headaches, seizures, confusion

  • Bone: Bone pain, fractures

  • Liver: Hepatomegaly, jaundice

  • Adrenal glands: Often asymptomatic but may cause adrenal insufficiency if bilateral


✅ Routes of Spread

  • Direct extension into adjacent structures (pleura, chest wall)

  • Lymphatic spread to hilar and mediastinal lymph nodes

  • Haematogenous spread to distant organs (brain, bone, liver, adrenals)


3. Paraneoplastic Syndromes by Cancer Type

Cancer Type

Syndrome

Cause

Symptoms

Treatment

Small Cell

SIADH

ADH secretion

Hyponatraemia – confusion, seizures

Fluid restriction, vasopressin antagonists, treat cancer

Small Cell

Cushing’s

ACTH secretion

Hypertension, hyperglycaemia, hypokalaemia

Cortisol synthesis inhibitors, treat cancer

Small Cell

LEMS

Anti-Ca channel antibodies

Proximal weakness improving with use, autonomic symptoms

Treat cancer, 3,4-DAP, immunotherapy

Squamous Cell

Hypercalcaemia

PTHrP secretion

Bone pain, constipation, confusion

IV fluids, bisphosphonates, treat cancer

Adenocarcinoma

HPOA

Growth factors

Clubbing, periostitis, arthralgia

NSAIDs, treat cancer


4. Risk Factors for Lung Cancer

✅ Smoking (most significant risk factor)

✅ Passive smoking

✅ Occupational exposures (asbestos, radon, arsenic, chromium, nickel)

✅ Air pollution

✅ Family history of lung cancer

✅ Pre-existing lung disease (COPD, pulmonary fibrosis)


5. Recommended Treatment Plan


Non-Small Cell Lung Cancer (NSCLC)

  • Early-stage (I-II): Surgical resection is preferred ± adjuvant chemotherapy/radiotherapy.

  • Locally advanced (III): Combination of chemotherapy and radiotherapy; surgery in selected cases.

  • Advanced (IV): Palliative chemotherapy, targeted therapy (e.g. EGFR inhibitors if positive), immunotherapy (e.g. pembrolizumab for PD-L1 positive tumours).


Small Cell Lung Cancer (SCLC)

  • Limited stage: Combination chemotherapy + radiotherapy.

  • Extensive stage: Chemotherapy is mainstay (e.g. platinum-based regimens). Prophylactic cranial irradiation is often used due to high risk of brain metastasis.


Key Takeaways for PLAB 2

✅ Always assess respiratory symptoms, systemic features, and risk factors in suspected lung cancer.

✅ Remember paraneoplastic syndromes as causes of non-respiratory presentations.

✅ Know the routes of metastasis and associated symptoms for differential diagnosis.

✅ Management depends on cancer type and stage, often involving a multidisciplinary approach with oncology, respiratory, and palliative care teams.


Final Tip

When examining a patient with unexplained systemic symptoms or risk factors such as heavy smoking, think lung cancer and its paraneoplastic manifestations as differentials in your PLAB 2 exam.


📚 References:

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