A 58-year-old man with a history of chronic cough and smoking (40 pack-years) presents with hemoptysis and dyspnea for 2 weeks. Chest X-ray shows a 3 cm right hilar opacity with associated atelectasis. Sputum cytology is pending. What is the most appropriate next imaging investigation to stage the disease and guide treatment planning?

Explanation

## Clinical Context The patient presents with a hilar mass in a heavy smoker with hemoptysis — highly suspicious for lung cancer. Staging and treatment planning require assessment of: 1. Local tumor extent 2. Mediastinal lymph node involvement 3. Distant metastases ## Why PET-CT is the Investigation of Choice **High-Yield:** PET-CT with 18F-fluorodeoxyglucose (18F-FDG) is the gold standard for staging suspected lung cancer because it simultaneously: - Characterizes the primary tumor (CT component) - Evaluates mediastinal and hilar lymph nodes for metastatic involvement - Detects distant metastases (bone, brain, adrenal, liver) - Guides biopsy and treatment planning **Key Point:** In a patient with suspected lung cancer and a hilar mass, PET-CT is essential because: - 18F-FDG uptake helps differentiate malignant from benign lesions - Identifies occult metastases in ~15–20% of patients with apparent early-stage disease - Determines TNM staging, which directly impacts treatment (surgery vs. chemoradiation) - Detects adrenal and bone metastases missed on CT alone **Clinical Pearl:** The combination of: - Smoking history (40 pack-years) - Hemoptysis (suggests central airway involvement) - Hilar opacity with atelectasis (suggests endobronchial obstruction) - Age 58 (peak incidence for lung cancer) ...makes lung cancer the primary differential diagnosis, and PET-CT is mandatory for staging. ## Comparison with Other Modalities | Modality | Role in Lung Cancer | Limitation in This Case | |----------|-------------------|-------------------------| | **PET-CT** | Gold standard for staging; detects metastases | None — essential for treatment planning | | **HRCT chest** | Excellent for local tumor and lung parenchyma | Does NOT detect distant metastases; poor for nodal staging | | **Bronchoscopy + EBUS** | Tissue diagnosis and local staging | Diagnostic tool, not for staging metastases; comes AFTER PET-CT | | **Lateral decubitus CXR** | Assesses pleural effusion mobility | Irrelevant; does not stage cancer | **Mnemonic:** **PET for Prognosis, Extent, and Therapy** — PET-CT provides the metabolic information needed to determine prognosis (stage), extent of disease, and whether the patient is a surgical candidate. **Tip:** The sequence in lung cancer workup is: 1. **CXR** (initial detection) ✓ Already done 2. **PET-CT** (staging and metastases) ← **Next step** 3. **Bronchoscopy ± EBUS** (tissue diagnosis and local staging) — after PET-CT 4. **Brain MRI** (if high-risk for CNS metastases) — if indicated by PET-CT