150P Assessment of high Ki67 (≥20%) ER+HER2- breast cancer with a 21-gene multigene assay

BackgroundKi67 immunohistochemistry (IHC) with a cut-off of 20% by MIB-1 PharmDx assay has been approved as companion diagnostic for adjuvant abemaciclib in high-risk ER+HER2- breast cancer. We addressed the genomic risk profile high Ki67 (≥20%) cancer using 21-gene multigene (Oncotype DX test). In addition, we investigated survival outcomes and identified factors associated low group.MethodsWe collected clinical pathologic information 2,295 patients who underwent Oncotype testing. High was defined recurrence score (RS ≥26). IHC examination performed locally MIB-1.ResultsThe assigned 870 (38%) to 1,425 (62%) groups, while RS 347 (15%) genomic-high 1,948 (85%) genomic-low. Of these, 263 (30%) had risk, whereas 84 1424 (6%) it (p<0.0001). Average significantly higher than Ki67. analyses, were significant prognostic factors. When classified into three groups (genomic-high, high-Ki67/genomic-low, low-Ki67/genomic-low), outcome high-Ki67/genomic-low better genomic-high, worse low-Ki67/genomic-low. Within group, multivariable analysis demonstrated that PR+, age ≤50, histologic grade I-II risk.ConclusionsAlthough about 60% tumors expression assay, have substantial relapse regardless risk. PR+ and/or lower grade, would be useful evaluate their risk.Legal entity responsible studyThe authors.FundingHas not received any funding.DisclosureAll authors declared no conflicts interest. group. MethodsWe MIB-1. ResultsThe The ConclusionsAlthough Although