P3-07-23: Intraoperative Molecular Analysis of Sentinel Lymph Nodes in Breast Cancer Using One Step Nucleic Acid Amplification (OSNA).

Abstracts: Thirty-Fourth Annual CTRC‐AACR San Antonio Breast Cancer Symposium‐‐ Dec 6‐10, 2011; San Antonio, TX Introduction: The OSNA method for the intra-operative analysis of sentinel lymph nodes (SLNs) in breast cancer has been introduced in 3 UK centres since 2007. The methodology uses a polymerase chain reaction to quantitate CK19, a cytokeratin specific to breast duct epithelial cells. OSNA provides “real-time” results on SLNs analysed as negative (−) or positive with either micro (+) or macrometastases (++). Method: This is a single-centre prospective pilot study of all patients undergoing breast cancer surgery including sentinel node biopsy from February 2010 to May 2011. SLN identification was performed using a dual localization technique with peri-areolar Patente V blue dye and Tc99 radio-active isotope. SLNs were cut into 4 slices labeled as A, B, C and D, respectively after the removal of all perinodal fat. In all SLNs, slices A and C were processed in OSNA and slices B and D underwent histological assessment by HE 23 mastectomies and 22 SLNB alone. The mean time for OSNA was 40.5, 51.8, 54 and 61.5 minutes for 1,2,3, and 4 sentinel lymph nodes respectively. Operation time was prolonged by a median of 20 minutes (range −48 to +65 minutes) WLEs were delayed by the greatest time Exclusions: Nodes that were not available for histological comparison i) nodes weighing <0.05g (n=34) were processed whole. ii) Departmental agreement from mid March 2011 to process nodes whole via OSNA (n=51); 6 had micro or macrometastases. Conclusion: OSNA prevented staged axillary surgery in 24 (21%) of patients. A median time of 20 minutes for the OSNA procedure is comparable with acceptable operating times. Current experience supports the use of OSNA for each individual whole SLN analysis. The pilot data has resulted in a prescribed change in policy to analyse the whole SLN using this technique. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-23.