Prevalence of Occult Peribronchial N1 Nodal Metastasis in Peripheral Clinical N0 Small (≤2 cm) Non-Small Cell Lung Cancer

Background: There has been growing interest in limited resection and nonsurgical treatment for small lung cancers. We examined the pattern and rate of occult N1 nodal metastasis in patients with peripheral, small (≤2 cm), clinically node-negative non-small cell lung cancer (NSCLC). Methods: Patients with peripheral small (≤2 cm) NSCLC with no evidence of locally advanced or metastatic disease (clinical T1a-b N0 M0, American Joint Committee on Cancer 8th Edition Cancer Staging Manual), who were deemed eligible for lobectomy or sublobar resection, were identified from preregistration eligibility screening logs for the Alliance/Cancer and Leukemia Group B 140503 trial at our institution. Pathologic outcomes were examined in all patients undergoing anatomic resection with mediastinal and hilar lymphadenectomy. Results: Included were 58 patients treated between November 2014 and January 2017 who met the inclusion criteria: 51 underwent lobectomy, and 7 underwent segmentectomy. Mean tumor diameter on computed tomography was 1.5 cm, and mean positron emission tomography maximal standardized uptake value was 3.9. The mean consolidation-to-tumor ratio was 0.77. Occult nodal metastases in N1 stations were found in 8 of 58 patients (14%), and most of these nodes were found in interlobar or peribronchial stations (11 or 12). An additional 2 patients (3%) had occult positive N2 nodes. Overall, the false-negative rate for clinical staging was 16%. Conclusions: Occult nodal disease was frequently identified in peripheral N1 stations (11-13) in patients with small (≤2 cm) clinical N0 NSCLC. Hilar lymphadenectomy is essential for accurate staging in the management of patients with small clinical N0 NSCLC.