Radioguided detection of lymph node metastasis in non-small cell lung cancer

The detection of micrometastases in thoracic lymph nodes may improve the staging of non-small cell lung cancer patients.

Ten patients with resectable lung cancers were enrolled in this pilot study. Every patient had preoperative positron emission tomography (PET) imaging and mediastinoscopy. Patients were injected with 10 mCi of F18-fluorodeoxyglucose (FDG) on the day of surgery, within 4 hours of the planned surgical procedure. A handheld device detected increased FDG uptake (gamma emission) within thoracic lymph nodes during pulmonary resection procedures. The lymph nodes that demonstrated increased FDG uptake, but were nonmalignant by conventional hematoxylin and eosin staining, underwent further serial sectioning and immunohistochemical staining.

The handheld probe detected all FDG-avid lesions on PET imaging. In 3 patients (30%), the probe led to the detection of FDG-avid lymph nodes harboring micrometastases missed by conventional pathologic analysis. A fourth patient had aortopulmonary nodes that were FDG-avid on PET and showed metastases by hematoxylin and eosin staining, but the probe detected adjacent nodes in the same station with micrometastases. Three nodes were false-positive by gamma probe.

It is feasible to detect occult metastases in lymph nodes by using an FDG-sensitive intraoperative gamma probe, resulting in upstaging of patients. A larger study is indicated to evaluate the sensitivity, specificity, and clinical utility of such a device.