115P Longterm prognostic utility of 70-gene signature by clinical and genomic risks, including Ultralow (gUL) risk patients (pts)

In the MINDACT trial, 4 risk categories (RC) by clinical (c) and genomic (g) risks were defined. cHigh/gLow patients (pts) with no adjuvant chemotherapy (CT), 8y-Distant Metastases Free Survival (DMFS) was 89.4 % [95% CI 86.2-91.5]. MP also identified a third subgroup of gUL pts (score 0.355 – 1.0, 15% in MINDACT), an excellent prognosis benefit from extended endocrine therapy (EET). We aimed to study: DFS/ DMFS 6 RC resulting combining 2 3 groups; timing recurrences; putative EET for each group. All ER+/HER2- BC data diagnosed between 2012-2017 at Vall d'Hebron University Hospital selected. cLow defined as trial. To study EET, landmark analysis 5y ET initiation conducted. 140 identified. Baseline features: 47.8% premenopausal; stage I/II: 74%/26%; histological grade 1/2/3: 19.6%/74.9%/6.5%. cLow/cHigh: 67%/33%; gUL/gLow-Non-Ultralow (LNUL)/gHigh: 11.4%/53.6%/35%. PgR Ki67 tended correlate g risks, but only IHC-subtype reached statistically significance. Systemic treatments [N/%]: 138/98.5%; ovarian function suppression premenopausal 23/35%; CT: 45/32%; EET: 49/35.8%. After 8y-median FU, 15 DFS events 11 observed. (UL+LNUL) without CT 90.6% [81.1%; 100%]. DFS/DMFS rates c/g category are depicted table. Only occurred after 5 years, precluding explore role RCTable: 115PcLow-gULcLow-gLNULcLow-gHighcHigh-gULcHigh-gLNULcHigh-gHighN (%)13 (9.4)45 (32)35 (25)3 (2.2)30 (22)13 (9.4)8y-DFS (%)1009184.81009076.9CI 95%-83.2-99.871.6-100-79.9-10057.1-1008y-DMFS (%)10095.589.11009084.6CI 95%-89.6-10077.7-100-79.9-10067.1-1008y-DMFS (%)cHigh-gLow No CT90.6% (CI 95% 81.1-100)8y-DMFS (%) Mindact TrialcHigh-gLow CT89.4% 86.2-91.5) Open table new tab . our series, rate cHigh-gLow similar that reported line prior reports, had survival, while cHigh-gHigh group showed significantly poorer outcome. Albeit limited small sample size, classification RCs instead seems useful redefine prognosis. Additional FU is warranted determine RC.