One-step nucleic acid amplification for detecting lymph node metastasis of head and neck cancer

Abstract

6028 Background: Lymph node stage is an important prognostic factor in squamous cell carcinoma of the head and neck (SCCHN). We previously reported the clinical usefulness of sentinel lymph node (SLN) biopsy diagnosed by concurrently performing histological examination using semiserial sections and genetic analysis by quantitative RT-PCR. However, these methods took about 3 hours. In this study, we have attempted to develop a more efficient method for intraoperative genetic detection of lymph node metastasis in SCCHN. Methods: A total of 291 lymph nodes (59 patients) resected on SLN biopsy for cN0 SCCHN or neck dissection for cN1/2 SCCHN were diagnosed by one-step nucleic acid amplification (OSNA) method using GD-100. The primary site was tongue, gingiva, oral floor, buccal mucosa, and pharynx in 44% (26), 37% (22), 10% (6), 5% (3), and 3% (2), respectively. OSNA consists of a short homogenization step followed by amplification of cytokeratin 19 (CK19) mRNA directly from the lysate. It is characterized by the use of 4 different primers specifically designed to recognize 6 distinct regions, so the CK19 primers do not amplify the known CK19 pseudogenes. The reaction process proceeds at a constant temperature (65°C) during strand displacement reaction. Amplification and detection of CK19 mRNA can be completed in a single step. Each lymph node was divided into two halves to diagnose metastasis. An alternative half was used for the OSNA assay with cytokeratin 19 (CK19) mRNA, and the remaining block was subjected to semiserial sectioning, sliced at 200-μm intervals and then examined by H&E and cytokeratin AE1/AE3 immunohistochemical staining. Results: Fifty-four of 291 lymph nodes were pathologically metastasis-positive. The optimal cut-off for the copy number of CK19 mRNA in assessing lymph node metastasis was 300 copies/μl, which had the highest diagnostic accuracy. The sensitivity and specificity of OSNA assay with CK19 mRNA was 92.6% (50/54) and 97% (230/237), respectively. An overall concordance rate between the OSNA assay and histopathology was 96.2%. The OSNA assay could be completed within 30 minutes. Conclusions: The OSNA assay showing high sensitivity and specificity can be used as a novel genetic detection tool of lymph node metastasis in SCCHN patients. No significant financial relationships to disclose.