Abstract P4-08-23: EndoPredict prognostic signature in pN1mi, estrogen receptor-positive breast cancer: analysis of the French national registry for molecular signatures
Authors: LaCroix-Triki M , Arnould L , MacGrogan G , Penault-Llorca F , Haudebourg J , Tas P , Garnier A , Vincent-Salomon A , Miquel C , Lehmann-Che J , Callens C , Quillien V , Cayre A , Lamy P-J , Rouleau E , De Cremoux P 
Published: May 2019

Abstract
Background
The EndoPredict (EP) test has been developed and validated for assessing recurrence risk in patients with estrogen receptor (ER)-positive HER2-negative breast cancer (BC). This test is based on the expression of 12 genes (molecular score), combined with clinicopathological criteria (i.e. tumor size and nodal status) (EPclin risk score). For node-positive patients, the weight given to the node status in the EPclin score is similar when considering pN1mi (]0.2-2mm]) or pN1 (&gt;2mm, 1-3 positive lymph nodes). Our aim was to characterize the EPclin classification of the pN1mi subgroup in the French national registry for molecular signatures in ER+ BC.
Methods
Since April 2016, nine French laboratories using EP test in clinical practice prospectively implement a national registry for molecular prognostic signatures in ER+ BC. We analyzed the pN1mi subgroup with regards to their clinico-pathological characteristics, molecular EP score and EPclin risk score. Using the definition formula of the EPclin score [EPclin=0.35t + 0.64n + 0.28EP, with n=1 for pN0, 2 for pN1mi/pN1, 3 for pN2, 4 for pN3], we could calculate a hypothetical EPclin score if the pN1mi had been considered as pN0 [n factor=1].
Results
By the end of 2017, the database included 1246 EP tests performed in routine practice, including 67 (5.4%) pN1mi. The pN1mi BC were ER+ HER2- (67/67, 100%), invasive carcinoma of no special type in 52/67 (78%), with a median tumor size of 18 mm (range 7-45; pT1c in 40/67). Among these, 22 were classified as EPclin low and 45 as EPclin high, with a median EP score of 6 (range 2-14), a median EPclin score of 3.70 (range 3-6), and a median relapse risk at 10-year of 15%(range 5-73). Most interestingly, 23/67 (34%; i.e. 1.8% of all EP tests performed) pN1mi BC displayed an EPclin score comprised between 3.4 and 4, just above the cut-off value of 3.3: these cases (and only these cases) would have been classified in a different risk category (i.e. EPclin low risk) if the node status would have been considered as negative.
Conclusion
With regards to EndoPredict test in pN1mi BC - and the persistent debate as to whether they should bear the same weight as node-positive (pN1) or negative (pN0) tumors - categorization in the EPclin class is not likely to be impacted by the node factor weight in the vast majority (&gt;65%) of the pN1mi cases and &gt;98% of all patients tested with EP. Only cases with an EPclin between 3.4 and 4 might be impacted.
Citation Format: LaCroix-Triki M, Arnould L, MacGrogan G, Penault-Llorca F, Haudebourg J, Tas P, Garnier A, Vincent-Salomon A, Miquel C, Lehmann-Che J, Callens C, Quillien V, Cayre A, Lamy P-J, Rouleau E, De Cremoux P. EndoPredict prognostic signature in pN1mi, estrogen receptor-positive breast cancer: analysis of the French national registry for molecular signatures [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-23.