Purpose: Lymph node metastases are the most significant prognostic factor in localized non-small-cell lung cancer (NSCLC). Nodal micrometastases may not be detected with current standard histologic methods. We performed intraoperative technetium-99m ((99m)Tc) sentinel lymph node (SN) mapping in patients with resectable NSCLC. This study aimed to identify the first station of nodal drainage of operable lung cancers. Serial section histology and immunohistochemistry were used to validate the SN and to identify the presence of micrometastatic disease.
Patients and methods: One hundred patients with potentially resectable suspected NSCLC were enrolled. At thoracotomy, the primary tumor was injected with 0.25 to 2 mCi (99m)Tc. Intraoperative scintigraphic readings of both the primary tumor and lymph nodes were obtained with a hand-held gamma counter. Anatomic resection with a mediastinal node dissection was then performed.
Results: Nine of the 100 patients did not have NSCLC (seven benign lesions and two metastatic tumors) and were excluded. Seventy-eight (86%) of 91 patients had a SN identified and a complete resection. Sixty-nine (88.5%) out of the 78 SNs were classified as true-positive with no metastases found in other intrathoracic lymph nodes without concurrent SN involvement. In nine patients, the SN was the only positive node. In seven of these nine patients, the SN was found to harbor only micrometastatic disease.
Conclusion: Intraoperative SN mapping with (99m)Tc is an accurate way to identify the first site of lymphatic tumor drainage in NSCLC. This method may also improve the precision of pathologic staging.