What is the purpose of Endobronchial Ultrasound (EBUS) in metastatic lung cancer?

Purpose of Endobronchial Ultrasound (EBUS) in Metastatic Lung Cancer

Endobronchial ultrasound (EBUS) is primarily used for accurate mediastinal nodal staging in metastatic lung cancer, allowing minimally invasive sampling of lymph nodes to confirm or exclude metastatic involvement, which is essential for determining optimal treatment strategies and reducing unnecessary surgeries.

Key Functions of EBUS in Metastatic Lung Cancer

Mediastinal Nodal Staging

• EBUS-TBNA (transbronchial needle aspiration) provides real-time visualization and sampling of mediastinal and hilar lymph nodes 1
• Allows access to key lymph node stations:
  • Stations 2L, 2R (upper paratracheal)
  • Stations 4L, 4R (lower paratracheal)
  • Station 7 (subcarinal)
  • Stations 10-12 (hilar and intrapulmonary nodes) 1
• Diagnostic yield of EBUS-TBNA for mediastinal staging reaches 88-92% sensitivity 1

Complementary Role with EUS (Endoscopic Ultrasound)

• Combined endosonography (EBUS-TBNA + EUS-FNA) increases diagnostic accuracy to 96% 1
• EUS can access stations that EBUS cannot easily reach:
  • Stations 8 and 9 (lower mediastinum)
  • Structures below the diaphragm (left adrenal, retroperitoneal nodes) 1, 2
• Combined approach allows sampling of virtually all mediastinal nodal stations 1

Tissue Acquisition for Molecular Testing

• EBUS provides sufficient tissue for both diagnosis and molecular analysis
• Guidelines recommend obtaining additional samples beyond those needed for diagnosis for molecular testing in non-small cell lung cancer 1
• This enables personalized treatment decisions based on molecular profiling

Clinical Indications for EBUS in Metastatic Disease

Abnormal Mediastinum on Imaging

• When CT or PET-CT shows enlarged (>10mm) or FDG-avid mediastinal lymph nodes 1
• EBUS is recommended as the initial test of choice over surgical staging 1

Normal Mediastinum with Risk Factors

• In patients with normal mediastinum but increased risk of mediastinal involvement:
  • Centrally located tumors
  • Hilar abnormalities 1
• EBUS is suggested over surgical staging in these cases 1

Restaging After Neoadjuvant Therapy

• For detecting persistent nodal disease following neoadjuvant therapy
• If EBUS is negative, subsequent surgical staging is still indicated 1

Diagnosis of Centrally Located Tumors

• For diagnostic purposes in centrally located lung tumors not visible at conventional bronchoscopy 1
• Particularly useful when tumors are adjacent to larger airways or esophagus 1

Advantages Over Surgical Staging

• Minimally invasive compared to mediastinoscopy
• Lower morbidity and cost 1
• Can be performed as an outpatient procedure with minimal sedation 1, 3
• Rare complications, with high safety profile 4, 3
• Cost-effective approach 1

Technical Considerations

Procedural Aspects

• Complete assessment should include sampling of at least three different mediastinal nodal stations (4R, 4L, 7) 1
• Sonographic features can help predict metastatic involvement:
  • Round shape
  • Distinct margin
  • Heterogeneous echogenicity
  • Presence of coagulation necrosis 5

Training Requirements

• Requires specific training and expertise
• Trainees should follow a structured curriculum with simulation-based training 1
• Competency should be assessed using validated assessment tools 1

Common Pitfalls and Limitations

• Cannot access all lymph node stations (particularly stations 5 and 6)
• Surgical staging may still be needed if EBUS results are negative in high-risk cases
• Operator dependence affects diagnostic yield
• Learning curve is substantial, requiring approximately 40 supervised procedures 1

EBUS has transformed the diagnostic approach to mediastinal and hilar diseases in lung cancer, providing a safe, accurate, and less invasive alternative to surgical staging while enabling both diagnosis and molecular characterization of metastatic disease.