A 62-year-old woman with a history of smoking presents with chest pain and dyspnoea. Chest X-ray reveals a large right hilar mass with mediastinal widening. Bronchoscopy is planned to assess for endobronchial involvement and obtain tissue diagnosis. Which investigation should be performed BEFORE bronchoscopy to assess mediastinal lymph node involvement and guide staging?

Explanation

## Investigation for Mediastinal Assessment in NSCLC ### Clinical Context The patient has a **large hilar mass with mediastinal widening**, suggesting possible mediastinal lymph node involvement (N2/N3 disease). Accurate staging is critical for treatment planning (surgery vs. chemoradiation). The question asks which investigation should be performed **before bronchoscopy** to assess mediastinal involvement. ### Why PET-CT with ¹⁸F-FDG? **Key Point:** **PET-CT is the single most important investigation for staging NSCLC** because it provides both anatomical (CT) and functional (metabolic) information, allowing detection of mediastinal lymph node involvement and distant metastases in a single study. **High-Yield:** PET-CT advantages: 1. **Detects metabolically active lymph nodes** — FDG uptake indicates malignancy (sensitivity ~85–90% for mediastinal nodes) 2. **Identifies distant metastases** — bone, liver, brain, adrenal (changes staging from local to stage IV) 3. **Non-invasive** — no general anaesthesia required 4. **Performed early** — guides decision between surgery, chemoradiation, or palliative care 5. **Guides further invasive staging** — if PET-positive mediastinal nodes, EBUS-TBNA or mediastinoscopy can be targeted ### Role of Each Investigation in Mediastinal Staging | Investigation | Timing | Purpose | Yield for Nodes | |---|---|---|---| | **PET-CT** | **First-line** | Whole-body staging; detect mets; metabolic assessment | ~85–90% sensitivity | | EBUS-TBNA | After PET-CT if nodes positive | Tissue diagnosis of PET-positive nodes | ~95% specificity | | Mediastinoscopy | If EBUS inconclusive or contraindicated | Surgical staging of anterior mediastinal nodes | Gold standard but invasive | | Chest CT alone | Baseline imaging | Anatomical detail; cannot assess metabolic activity | Limited for node staging | **Clinical Pearl:** The **staging algorithm** for NSCLC is: 1. **PET-CT** (first-line, non-invasive, whole-body) 2. If PET-positive mediastinal nodes → **EBUS-TBNA** (tissue diagnosis, minimally invasive) 3. If EBUS non-diagnostic or contraindicated → **Mediastinoscopy** (gold standard, but requires GA) ### Why PET-CT Before Bronchoscopy? **Key Point:** PET-CT should be performed **before bronchoscopy** because: - It provides **staging information** that may change management (e.g., discovery of distant metastases makes surgery futile) - It **guides tissue sampling** — EBUS-TBNA can target PET-positive nodes - Bronchoscopy is a **diagnostic/therapeutic tool** for endobronchial disease, not staging **Mnemonic: STAGING NSCLC — PET-CT First** - **P**ET-CT: whole-body staging, metabolic activity - **E**BUS-TBNA: tissue diagnosis of PET-positive nodes - **T**horacotomy/mediastinoscopy: if staging incomplete [cite:Harrison 21e Ch 297]