Background:

Lymph node staging provides the most important prognostic information in patients with loco-regional non-small cell lung cancer. We hypothesized that gamma radiation detection using an intra-operative hand-held gamma probe following intravenous 18F-fluorodeoxyglucose (FDG) injection would identify lymph nodes containing metastases in a much more sensitive manner than standard pathological practices. We compared the accuracy of detecting thoracic lymph node metastases using positron emission tomography- computed tomography (PET-CT) versus the gamma probe.

Methods:

One hundred patients with resectable lung cancers had pre-operative positron emission tomography-computed tomography (PET-CT) and mediastinoscopy. 10mCi of FDG was injected on the day of surgery. A handheld gamma probe detected increased FDG uptake within thoracic lymph nodes during pulmonary resection procedures. The lymph nodes that demonstrated increased FDG uptake, but were non-malignant by conventional H&E staining underwent further serial sectioning, immunohistochemistry (IHC) and RT-PCR (reverse transcriptase - polymerase chain reaction). Sensitivity and specificity for lymph node metastasis detection by PET-CT and the gamma probe were calculated.

Results:

Three patients had metastatic lymphadenopathy detected at mediastinoscopy, so their procedures were aborted, while the others proceeded to lung resection and complete lymphadenectomy. Fifteen additional patients had lymph node involvement on routine pathologic analysis. IHC and RT-PCR detected micrometastatic lymph node disease in 4 and 29 patients, respectively. Using RT-PCR as the gold standard, the sensitivity and specificity of PET-CT for detection of lymph node metastasis were 11% and 98% respectively, in contrast to 38% and 50% respectively for the gamma probe.

Conclusion:

The intra-operative hand held gamma probe is more sensitive but less specific than PET-CT in detecting lymph node metastasis from lung cancer. Its overall accuracy was low, resulting in limited up-staging of patients. RT-PCR analysis of FDG-avid lymph nodes for epithelial markers increased the clinical utility of this probe in detecting micrometastasis. Such up-staged patients could derive a survival benefit from adjuvant chemotherapy. More specific radioisotopes are being developed to improve the clinical utility of this technique.

Citation Format: Chukwumere Nwogu, Todd Demmy, Sai Yendamuri, Wei Tan, Paul Bogner, Elisabeth Dexter, Anthony Picone, Mark Hennon, Alan Hutson, Mary Reid, Richard Cheney, Alex Adjei. Radioguided detection of lymph node metastasis in non-small cell lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4671. doi:10.1158/1538-7445.AM2013-4671