Abstract P2-01-17: Total tumoral load as a prediction tool of non-sentinel node metastases in patients with early breast cancer and positive sentinel lymph node assesed by OSNA
Authors: Espinosa-Bravo Martin , Pérez-Ceresuela Francesc , Diaz-Botero Sebastian , Peg Vicente , Rubio Isabel T 
Published: May 2015

Abstract
Background: Total tumoral load (TTL) in the sentinel lymph nodes (SLN) assessed by the OSNA assay is a new variable that is able to predict the likelihood of more axillary metastasis. Compared with the number of positive SLNs, the TTL is independent of the number of metastatic SLNs and a better predictor of further nodal metastasis. Although establishing specific cutoff-points of the TTL can be questionable because they may change in the future and increasingly become more patient specific, we have seen that TTL &lt;15.000 could be a good cut off by its high negative predictive value (NPV). Changes in practice have been occurred after the ACOSOG Z0011 trial and nowadays, patients with ≤ 2 positive SLNs may spare an axillary lymph node dissection (ALND) with no impact on the oncological outcome. In the Z0011, 27% of patients had additional non-SLN metastasis in the cALND. The objective of this study was to compare two methods of SLN metastatic burden, the TTL and the number of positive SLNs, for predicting non-SLN metastasis in patients with positive SLNs by OSNA.
Methods: This is a retrospective cohort study of 145 consecutive patients with cT1-T2 invasive breast cancer with ultrasonographically node-negative treated between April 2010 to April 2013, where there is at least one positive SLN assesed by OSNA. We design a prediction tool based on the TTL results determined by OSNA to calculate the likelihood of not finding more positive non-SLN (http://www.vhebron.net/es/calculadora-risc-metastasi-2). Our group have demonstrated that TTL=15.000 could be a good cut off by its high NPV and sensitivity, 85.5% and 76.7%, respectively.
Results: A total 325 SLNs were removed with a mean of 2.24. The type of SLN metastasis were macrometastasis in 85 patients (58.6%) and micrometastasis in 60 patients (41.4%). When considering patients with number of positive SLNs, of 109 patients with ≤2 positives SLNs and an cALND, 17 patients (22%) had non-SLN metastasis; and of 5 patients with ≥3 SLN, four (80%) had non-SLN metastasis. Taking the TTL results, of 51 patients with TTL &lt;15.000 copies/µL with cALND (90.2% with one positive SLN), 7 patients (14%) had non-SLN metastasis, were a media of 2.2 extra non-SLN metastasis.
Of 55 patients with TTL ≥15.000 copies/µL (with 1 or 2 positives SLNs) with cALND, 20 patients (36%) had non-SLN metastasis and there were a media of 2.5 non-SLN metastasis (range 1-8). Of 34 patients (62%) with one positive SLN with TTL ≥15.000 copies/µL, 12 patients (35%) had non-SLN metastasis; and of 21 patients with two positive SLN with TTL ≥15.000 copies/µL, eight patients (38%) had non-SLN metastasis.
Conclusion: The total tumor load obtained by OSNA predicts non-SLN metastasis independent of the number of positive SLNs. The assess of the TTL in our cohort of patients show that patients with one or two positives SLNs with high TTL had high likelihood of non-SLN metastasis greater than 27% of Z0011 criteria. Prospective studies are needed to determine the clinical impact of this variable in patients outcome in the management of patients with SLN assesed by OSNA.
Citation Format: Martin Espinosa-Bravo, Francesc Pérez-Ceresuela, Sebastian Diaz-Botero, Vicente Peg, Isabel T Rubio. Total tumoral load as a prediction tool of non-sentinel node metastases in patients with early breast cancer and positive sentinel lymph node assesed by OSNA [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-01-17.