[258] Multicentric Comparative Study between One-Step Nucleic Acid Amplification (OSNA) Whole Node Assay and Standard Histology for Breast Sentinel Lymph Node: Molecular Assay Can Avoid Secondary Surgeries and Predict No Other Node Involvement

Irene Sansano, Martin Espinosa, Carmela Iglesias, Miren Aizpurua, Magdalena Sancho, Carmen Garcia, Isabel Rubio, Santiago Ramon y Cajal, Vicente Peg. H. U. Vall d'Hebron, Barcelona, Spain; H. de Salamanca, Salamanca, Spain

Background: Although the sentinel lymph node (SLN) biopsy is a common procedure in the management of early stage breast cancer, SLN examination has not been standardized. Recently, the OSNA is being considered as a potential standard method, providing a semi-quantitative result in a short period of time according to the amount of CK19 mRNA copy number. The aims of this study were, first, to compare SLN intraoperative assessment with OSNA assay using a whole lymph node versus routine H&E frozen section (FS) and final histological diagnosis with a 2 mm-sectioned lymph node and second, to evaluate the ability of the molecular assay to predict non-SNL involvement.
Design: A cohort of 609 consecutive patients diagnosed between 2010 and 2011 with early breast cancer in two centers (H. de Salamanca, H.U. Vall d'Hebron, Barcelona) were analyzed. FS was performed intraoperatively in 303 patients and OSNA assay in 306 patients. Patients' characteristics were evaluated in both groups and rates of metastasis detected by both methods were compared. A lymphadenectomy was performed in all cases with SLN involvement detected either by OSNA or histology and non-SLN were only analyzed with H&E (1mm section).
Results: SLN metastasis was found in 80 cases (26,4%) by conventional H&E analysis and in 108 (35,3 %) by OSNA (p=0.068). 32 of the 80 positive cases (40%) from the FS group were only found after final histological evaluation (formalin fixed paraffin embedded blocks). 30 lymphadenectomies performed in the OSNA group showed non-SLN involvement (27,8%). Considering the amount of mRNA CK19 copies number in all positive SLNs per patient (total tumoral load (TTL)), 150000 copies cut-off was able to predict negative axillary dissections (negative predictive value=0,79, specificity=0,85, sensibility=0,43, p=0,02).
Conclusions: First, with the OSNA method there was a higher sensitivity in detecting metastasis than with conventional H&E. Despite this difference was not statistically significant (p=0,068), the molecular assay would have avoided second-time axillary dissection in 40% of positive cases from the FS group. Second, total amount of CK19 mRNA copies number was a good predictor of no further nodal involvement. However, real clinical value of TTL remains unknown. A recent multicentric study (B-CLOSER II) has just started, to try to answer this question.
Category: Breast

Monday, March 19, 2012 2:30 PM

Platform Session: Section B, Monday Afternoon


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