In lung cancer staging, what is the primary purpose of EBUS?

• A. Detect distant metastases
• B. Assess mediastinal lymph node involvement
• C. Measure tumor size
• D. Evaluate brain metastases

Answer: (B)

The main concept being tested is how EBUS is used to stage lung cancer by checking mediastinal lymph node involvement. Endobronchial ultrasound combines a bronchoscope with ultrasound to visualize lymph nodes near the trachea and main bronchi. If a node looks suspicious, a needle can be guided through the airway wall into the node to obtain cells for analysis (EBUS-TBNA). This directly informs the N stage of cancer, which is essential for deciding treatment options, such as surgical resection versus chemoradiation, and for prognosis.

Distant metastases and brain metastases require other imaging methods beyond EBUS, like PET-CT or MRI, and tumor size is typically measured on CT or MRI scans. So the primary purpose of EBUS in staging is to assess mediastinal lymph node involvement.