Background: New molecular techniques have been designed to detect cancer micrometastases that are otherwise missed by conventional histologic examination. The aim of this study was to establish a sensitive and rapid genetic assay to detect lymph node micrometastasis and to assess its usefulness clinically for cervical lymphadenectomy in esophageal cancer. We have recently shown that metastasis in the lymph node chain along the recurrent laryngeal nerves (rec LNs) is a predictor of cervical node metastasis in esophageal cancer. In our retrospective study, the positive rate of cervical lymph node metastasis with rec LNs metastasis was 51.6%, and the rate without rec LNs metastasis was 11.6%. There was a significant difference in both positive rates (P =.0002).
Methods: Rec LNs obtained from 50 patients with esophageal cancer were assessed prospectively by intraoperative histopathologic examination (HE) and genetic analysis. The latter involved a real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) system with multiple markers, carcinoembryonic antigen, squamous cell carcinoma, and melanoma antigen-3, whose messenger RNAs are highly and frequently expressed in esophageal cancers. Cervical lymphadenectomy was subsequently performed in a subset of these patients.
Results: Ten of 50 patients (20%) were scored as node positive by HE, and 24 patients (48%) were scored positive by genetic diagnosis, including 9 HE-positive cases. Genetic diagnosis of rec LNs accurately predicted all 9 cases with cervical lymph node metastasis and 2 cases with cervical lymph node recurrence, whereas HE missed 2 cases with cervical lymph node metastasis and 2 cases with cervical lymph node recurrence.
Conclusions: Our real-time rapid RT-PCR assay can improve the sensitivity of HE for detection of lymph node metastasis and might be potentially useful for intraoperative genetic diagnosis for subsequent cervical lymphadenectomy in esophageal cancer surgery.