Patients with radiological N0 disease without distant metastasis either underwent pre-operative EBUS-TBNA or directly proceeded to surgical resection at the discretion of attending physicians, since there was no consistent indication for pre-operative EBUS-TBNA in patients with radiological N0 disease. EBUS-TBNA was performed with a convex probe EBUS bronchoscope (BF-UC260F-OL8; Olympus, Tokyo, Japan) and a 22-gauge needle (NA-201SX-4022; Olympus) under moderate sedation with intravenous midazolam and fentanyl. After systematic inspection of lymph node stations, each visible lymph node was sampled in the standard N3 to N2 to N1 fashion, with size cut-offs of ≥5 mm in the short axis by EBUS. We conducted three passes per node and at least two passes when core tissue was obtained [17 (link), 18 (link)]. Transoesophageal bronchoscopic ultrasound-guided fine-needle aspiration (EUS-FNA-B) using the EBUS bronchoscope was done in selected cases [19 (link)]. Rapid on-site cytopathological evaluation was not available. When the clinical suspicion of mediastinal metastasis remained high despite a negative result in EBUS-TBNA, pre-operative mediastinoscopy was performed. Otherwise, surgical resection with MLND was considered if there was no metastasis to mediastinal lymph nodes in EBUS-TBNA.
The surgical procedures included resection of the affected lung plus lymph node dissection of the ipsilateral hilum and mediastinum, including all visible and palpable lymph nodes irrespective of size [20 (link), 21 (link)]. MLND consisted of en bloc resections of all nodes at stations 10R, 9, 8, 7, 4R, 3 and 2R for right-sided tumours and nodes at stations 10L, 9, 8, 7, 6, 5 and 4L for left-sided tumours.