Rapid molecular detection of metastatic head and neck squamous cell carcinoma as an intraoperative adjunct to sentinel lymph node biopsy

Objectives/hypothesis: Clinical staging of early head and neck squamous cell carcinoma (SCCHN) is often inaccurate, leading to elective neck dissection to detect the 30% of patients with micrometastatic disease. Sentinel node biopsy accurately stages the regional lymphatics, but intraoperative pathology is only moderately sensitive, and final pathology takes several days to complete. To facilitate immediate neck dissection where necessary, we have identified several promising marker genes of SCCHN metastasis and developed a rapid, accurate, and automated quantitative real-time polymerase chain reaction (PCR) (qRT-PCR) assay for intraoperative use.

Study design: Prospective tissue collection, retrospective pathologic correlation with qRT-PCR.

Methods: From a 40-gene marker screen, we quantified expression of 11 potential tumor genes using a test set of primary tumors (n = 32) and metastatic (n = 19) and benign (n = 10) lymph nodes. Eight patients' paired primary tumor and metastatic nodes were included. A validation set of 442 grossly tumor-negative nodes was evaluated for expression of the most promising markers, comparing metastasis detection by qRT-PCR with pathologic analysis (hematoxylin and eosin and immunohistochemistry). A novel multiplexed, automated, single-tube qRT-PCR assay was used to analyze more than 100 lymph nodes using a two-marker, 35-minute assay to determine its negative predictive value.

Results: Based on expression of 11 tumor-associated genes from the marker screen, the two most promising markers of SCCHN metastasis in the test set, pemphigus vulgaris antigen (PVA) and tumor-associated calcium signal transducer 1 (TACSTD1), also known as epithelial cell adhesion molecule (EpCAM), were selected. Development of a multiplexed qRT-PCR assay for the detection of metastasis compared favorably with pathologic analysis in the additional 442-node set. A rapid, multiplexed assay using PVA and TACSTD1 demonstrated excellent reproducibility, linearity, and accuracy (≈96% negative predictive value) for identifying positive (n = 40) and negative (n = 62) nodes in a validation subset.

Conclusions: Detection of metastatic SCCHN using multiplexed qRT-PCR can be rapid, accurate, and automated and may enable sentinel node biopsy to be used for intraoperative decision-making. PCR amplification of tumor marker genes is an effective method of intraoperative molecular staging of SCCHN and could more appropriately guide application of neck dissection in pN+ SCCHN patients, sparing 60% to 70% of pN0 patients from unnecessary neck dissection. This technique may also be used for identifying residual neck disease posttreatment, using outpatient fine-needle aspiration biopsy specimens.