Intraoperative radioisotope sentinel lymph node mapping in non–small cell lung cancer

Background. Lymph node metastases are the most significant prognostic factor in localized non–small cell lung cancer (NSCLC). Nodal micrometastases may not be detected. Identification of the first nodal drainage site (sentinel node) may improve detection of metastatic nodes. We performed intraoperative Technetium 99m sentinel lymph node (SN) mapping in patients with resectable NSCLC. Methods. Fifty-two patients (31 men, 21 women) with resectable suspected NSCLC were enrolled. At thoracotomy, the primary tumor was injected with 2 mCi Tc-99. After dissection, scintographic readings of both the primary tumor and lymph nodes were obtained with a handheld gamma counter. Resection with mediastinal node dissection was performed and findings were correlated with histologic examination. Results. Seven of the 52 patients did not have NSCLC (5 benign lesions, and 2 metastatic tumors) and were excluded. Forty-five patients had NSCLC completely resected. Mean time from injection of the radionucleide to identification of sentinel nodes was 63 minutes (range 23 to 170). Thirty-seven patients (82%) had a SN identified; 12 (32%) had metastatic disease. 35 of the 37 SNs (94%) were classified as true positive with no metastases found in other intrathoracic lymph nodes without concurrent SN involvement. Two inaccurately identified SNs were encountered (5%). SNs were mediastinal (N2) in 8 patients (22%). Conclusions. Intraoperative SN mapping with Tc-99 is an accurate way to identify the first site of potential nodal metastases of NSCLC. This method may improve the precision of pathologic staging and limit the need for mediastinal node dissection in selected patients.