Preparatory Mindset
Lung cancer is the leading cause of cancer death — in China ~23.9% of all malignant-tumour deaths — and smoking is responsible for ~87% of cases. The exam approach: (1) histology first — NSCLC (~75–80%: adenocarcinoma ~40%, squamous ~25%, large cell) vs SCLC (~15–20%), because treatment and prognosis differ radically (SCLC = chemotherapy/radiotherapy-centric, paraneoplastic-prone); (2) recognise the clinical presentations — central tumour (cough, hemoptysis, wheeze, SVC syndrome) vs peripheral (pleuritic pain, effusion), plus paraneoplastic syndromes (SIADH, hypercalcaemia via PTHrP in squamous, Eaton-Lambert in SCLC, Horner/Pancoast in superior sulcus tumours); (3) stage before treatment (TNM; CT ~95% sensitivity, PET ±8% false rates, tissue confirmation via bronchoscopy/FNA/CT-guided biopsy). LMCHK note: the handbook addresses preoperative pulmonary-function evaluation for lung-cancer resection — know the FEV₁/DLCO thresholds.
Core Concepts
Definition & epidemiology
- Bronchogenic carcinoma = primary malignant tumour of the lung arising from bronchial epithelium.
- China: lung cancer deaths = 23.9% of total malignant-tumour deaths; 5-year relative survival ~15.7% (1995–2001) improving to ~28.7% (2019–2021); stage-dependent 5-year survival ~49% (localised) → 16% (regional) → 2% (distant).
- Smoking: ~87% of lung cancers smoking-related; causes ~90% of male and 75–80% of female lung-cancer deaths; secondhand smoke (ETS) → ~20% of lung cancers, +20–30% risk for non-smoking cohabitants; risk declines after >5 years cessation; 80–90% risk reduction at 15 years.
Histological classification & key features
| Type | Frequency | Key features |
|---|---|---|
| Adenocarcinoma | ~40% (most common) | Peripheral, non-smokers/females; associated with EGFR/ALK mutations (targetable); lepidic growth |
| Squamous cell carcinoma | ~25% | Central (50% arise from major bronchi); cavitation; hypercalcaemia (PTHrP); strongly smoking-related |
| Large cell carcinoma | ~10% | Undifferentiated; peripheral, large mass |
| SCLC | ~15–20% | Central, neuroendocrine; most aggressive (rapid growth, early metastasis); paraneoplastic (SIADH, Eaton-Lambert); treated with chemo ± RT (rarely surgical) |
| Neuroendocrine tumours (total) | ~20% | Most (≈15%) are SCLC |
Clinical presentation
- Central tumour (bronchial): persistent cough, hemoptysis, wheeze/stridor, dyspnoea; obstructive pneumonia/atelectasis; SVC syndrome (facial/upper-limb oedema, dilated chest veins); hoarseness (recurrent laryngeal nerve).
- Peripheral tumour: pleuritic chest pain, persistent cough, haemoptysis, dyspnoea; pleural effusion.
- Superior sulcus (Pancoast) tumour (apical): shoulder/arm pain (brachial plexus), Horner syndrome (ptosis, miosis, anhidrosis), rib erosion.
- Metastatic disease: brain (headache, seizures), bone (pain, pathological fracture), liver, adrenal.
- Paraneoplastic syndromes (high-yield): SIADH (hyponatraemia — SCLC), hypercalcaemia (PTHrP — squamous), Eaton-Lambert myasthenic syndrome (SCLC — proximal weakness, improves with activity), digital clubbing, hypertrophic pulmonary osteoarthropathy, hypercoagulability (Trousseau).
- Majority symptomatic at presentation (>85%).
Diagnosis & staging
- CXR: initial screen — misses 10–20% of small cancers.
- CT chest: sensitivity ~95% for cancer detection (false-positive ~8%, false-negative ~8%).
- PET-CT: staging (nodal/distant disease) — metabolically active tissue; false positives (infection/inflammation) and negatives (small/low-grade).
- Tissue diagnosis: sputum cytology; bronchoscopy with brushing/BAL/biopsy (sensitivity central lesions 75–100%, larger peripheral 60–70%); CT/US-guided FNA or core biopsy (peripheral ~90% sensitivity); EBUS-TBNA for mediastinal nodes; pleural fluid cytology.
- Staging: TNM system (T — primary tumour: T2/T3/T4 by size/invasion; N — nodes; M — metastases) → groups into stages I–IV; CT/PET for distant mets; brain MRI if neurological symptoms/SCLC staging.
- Differential: COPD/benign nodules, tuberculosis (cavitating mass — irregular cavity wall suggests necrotic neoplasm), pneumonia not resolving, hamartoma, metastasis from other primaries.
Treatment
- Early (I–II): surgical resection (lobectomy) ± adjuvant chemo; stereotactic RT if unfit. - Locally advanced (III): chemo-radiotherapy ± immunotherapy; surgery in selected. - Metastatic (IV): platinum-based chemo + immunotherapy; targeted therapy if EGFR/ALK/ROS1 mutation; palliative RT (bone/brain), symptom control.
- NSCLC (by stage + molecular profile):
- SCLC: chemo (platinum-etoposide) + RT (thoracic); prophylactic cranial irradiation for good responders; immunotherapy add-on; palliative care. Surgery only for very early limited SCLC (rare).
- General: smoking cessation, supportive/palliative care (pain, dyspnoea, hemoptysis), clinical trials.
HKHA Handbook (LMCHK) — Key Points
- Preoperative evaluation of pulmonary function for resection of lung cancer (P 19): operable patients must be assessed for resectability by FEV₁ and DLCO — pneumonectomy generally requires FEV₁ (and DLCO) >40% predicted post-resection predicted values; lobectomy >30–40%; borderline cases need cardiopulmonary exercise testing (VO₂max). This is the LMCHK-relevant lung-cancer item in the handbook (no dedicated oncology-respiratory chapter).
- Massive haemoptysis (P 1): in lung cancer/malignancy — secure airway, reverse coagulopathy, bronchial artery embolisation, consider surgery for massive haemoptysis.
- Dyspnoea in advanced cancer (PM 8–9): manage reversible causes (effusion, obstruction, infection), opioids for breathlessness, palliative strategies.
- Metastatic spinal cord compression / malignant hypercalcaemia / SVC obstruction — palliative medicine sections (PM) cover these emergencies which complicate lung cancer.
High-Yield Points
- NSCLC ~75–80% (adenocarcinoma ~40% — peripheral, non-smoker; squamous ~25% — central, hypercalcaemia); SCLC ~15–20% — central, neuroendocrine, chemo-sensitive.
- Smoking ~87%; ETS ~20%; risk drops after >5 years cessation.
- Paraneoplastic: SIADH + Eaton-Lambert (SCLC); hypercalcaemia PTHrP (squamous); Horner/Pancoast (apical).
- CXR misses 10–20% of small cancers; CT ~95% sensitive; PET ~8% FP/FN.
- Bronchoscopy: central 75–100%; FNA peripheral ~90%.
- SCLC → chemo + RT + PCI; NSCLC → surgery early, targeted therapy if EGFR/ALK, immunotherapy.
- Preop lung-cancer resection: FEV₁/DLCO + CPET thresholds (HKHA P 19).
Topic Summary
Lung cancer — the leading cancer killer, ~87% smoking-related — is managed by first establishing histology (NSCLC vs SCLC: adenocarcinoma now most common and targetable, squamous central with hypercalcaemia, SCLC neuroendocrine and chemo-radiosensitive), then recognising the presentation (central vs peripheral vs paraneoplastic: SIADH, Eaton-Lambert, PTHrP hypercalcaemia, Pancoast/Horner), and staging with CT/PET and tissue confirmation (bronchoscopy, FNA). Treatment is stage- and histology-driven: surgery for early NSCLC, chemo-radiotherapy ± immunotherapy for SCLC and advanced disease, with targeted therapy for EGFR/ALK mutants. The HKHA handbook's pre-operative pulmonary-function thresholds for resection (FEV₁/DLCO, CPET) are the LMCHK-specific must-know.