Feasibility of intraoperative indocyanine green injection to identify lymph nodes at risk of metastatic disease for early-stage lung cancer.

Objectives: Despite surgical resection and mediastinal lymph node dissection, 34% of patients with stage IB to IIB non-small cell lung cancer demonstrate recurrence within 3.5 years, indicating disease dissemination undetected by current staging methods. Although 23.1% of patients with clinical N0 disease are upstaged to pN1 or pN2 disease after surgery, occult disease may still be present in patients with pN0 disease. The aim of this research was to explore implementation of a sentinel lymph node (SLN) procedure to identify lymph nodes at risk and determine its effect on staging. Methods: In this single-center prospective study, patients with cN0 disease with resectable non-small cell lung cancer underwent intraoperative indocyanine green injection followed by the identification of up to 3 SLNs with near-infrared imaging. All lymph nodes were analyzed by conventional hematoxylin and eosin staining and the SLNs were additionally analyzed by serial sectioning and cytokeratin staining to detect tumor cells that may be missed by conventional analysis. Results: SLNs were successfully identified in all 48 patients (100%). In 3 cases, injections were incorrectly positioned, possibly leading to incorrect SLN identification. Eight patients were diagnosed with pN1 or pN2 disease postoperatively; all were detected by conventional pathological assessment. Analysis of correctly performed SLN procedures showed negative SLNs were 100% indicative of absence of metastatic spread downstream. In 2 patients, serial sectioning and cytokeratin staining of the SLN revealed isolated tumor cells in 1 N1 node. Conclusions: An intraoperative SLN procedure using indocyanine green is feasible with an identification rate of 100%. A negative SLN was an indicator for absence of metastases in lymph nodes downstream.