Intraoperative molecular sentinel lymph node analysis with OSNA: multicentre prospective UK evaluation.

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #1003 Introduction: Rapid intraoperative molecular analysis of sentinel lymph nodes (SLNs) in breast cancer (BC) patients has the advantage of providing the surgeon with an immediate automated result, without the opinion of a consultant histopathologist, allowing axillary dissection to proceed in SLN positive patients. We undertook a multicentre, prospective evaluation of the OSNA system (One Step Nucleic Acid Amplification) for molecular analysis, to evaluate this new diagnostic technique's accuracy and feasibility for use in our hospital system. This abstract reports our 'Phase 2 - Intraoperative' experience. Method: Four study centres, both district general and major teaching hospitals took part in the evaluation. SLNs from breast cancer patients were excised using standard surgical techniques. Fresh SLNs were defatted and cut into 4 x 1 or 2mm slices depending on size and weight. Alternate slices underwent lysate preparation and immediate OSNA molecular analysis (detection and amplification of CK19 mRNA); remaining slices were processed for permanent section - intensive haematoxylin & eosin and immunohistochemistry (CK19 and AE1/AE3) examination (25μm multistep sections, 5 levels). OSNA results were correlated with final histopathology findings. Processing times were also recorded. No clinical decision was made based on the intraoperative OSNA result. Results: 396 lymph node samples were included in the analysis. Concordance with histopathology was 96.2% overall with all sites reaching concordance >95%. Overall sensitivity was 91.5%, specificity 97.2%, positive predictive value 87.7%, negative predictive value 98.1%. Concordance of OSNA with histopathology for lobular carcinoma (34 SLN samples) was >95%. There were 14 cases of tissue allocation bias confirmed on repeated molecular and histology testing that were excluded from overall results. Minimum time to reach a result on a single node was 22 minutes. Conclusion: The OSNA molecular system for SLN diagnosis provides an accurate and feasible intraoperative assessment of SLN status, achieving consistent results across multiple centres. This system may replace current histopathology-based techniques for intraoperative SLN analysis due to high concordance with histology and that it does not require input from a consultant pathologist. OSNA could allow more breast cancer patients in the UK access to one step axillary surgery. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1003.