The diagnostic accuracy of reverse transcription-PCR quantification of cytokeratin mRNA in the detection of sentinel lymph node invasion in oral and oropharyngeal squamous cell carcinoma: A comparison with immunohistochemistry

Purpose: The main goal of sentinel lymph node (SLN) detection in head and neck squamous cell carcinomas is to limit neck dissections to pN+ cases only. However, intraoperative+diagnosis cannot be routinely done using the current gold standard, serial step sectioning with immunohistochemistry. Real-time quantitative reverse transcription-PCR (RT-PCR) is potentially compatible with intraoperative use, proving highly sensitive in detecting molecular markers. This study post-operatively assessed the accuracy of quantitative RT-PCR in staging patients from their SLN. Experimental Design: A combined analysis on the same SLN by serial step sectioning with immunohistochemistry and quantitative RT-PCR targeting cytokeratins 5, 14, and 17 was done in 18 consecutive patients with oral or oropharyngeal squamous cell carcinoma and 10 control subjects. Results: From 71 lymph nodes examined, m RNA levels (KRT) were linked to metastasis size for the three cytokeratins studied (Pearson correlation coefficient, r=0.89, 0.73, and 0.77 for KRT 5, 14, and 17 respectively; P<0.05). Histopathology-positive SLNs (macro- and micrometastases) showed higher mRNA values than negative SLNs for KRT 17 (p<10(-4)) and KRT 14 (p<10(-2)). KRT 5 showed nonsignificant results. KRT17 seemed to be the most accurate marker for the diagnosis of micrometastases of a size >450 mu m. Smaller micrometastases and isolated tumor cells did not provide results above the background level. Receiver operating characteristic curve analysis for KRT 17 identified a cutoff value where patient staging reached 100% specificity and sensitivity for macro- and micrometastases. Conclusion: Quantitative RT-PCR for SLN staging in cN(0) patients with oral and oropharyngeal squamous cell carcinoma seems to be a promising approach.