Reflex MammaPrint testing on breast core biopsies: A single center experience.

Abstract

e12581 Background: Breast cancer genomic assays are well established in the adjuvant setting, but still evolving in the neoadjuvant setting. Recent data shows that MammaPrint (MP)/BluePrint (BP) genomic assays in the neoadjuvant setting can reclassify hormone receptor positive (HR+), HER2 negative (HER2-) tumors into intrinsic phenotypes with corresponding responses to neoadjuvant therapy (NAC). We performed reflex MP/BP assays on invasive breast cancer core biopsies and evaluated the relationships between clinical risk, molecular risk and intrinsic phenotype. Methods: 150 consecutive HR+, HER2- invasive breast cancers were identified by core biopsy in a tertiary care cancer center and underwent reflex MP/BP testing by an external central laboratory between July 2021 and Jan 2022. Retrospective review was completed on patient demographics and tumor characteristics; descriptive statistics were performed. Results: Of 150 newly diagnosed HR+ HER2- breast cancers, 141 successfully had a reflex MP/BP test performed; 9 were not performed due to technical feasibility or clerical error. Of the 141 patients with a completed MP/BP assay, 7 had recurrent disease, and 8 had metastatic disease, these were excluded. Patients were categorized as clinically high (cHR) or low risk (cLR) using the criteria from the MINDACT trial and as molecularly high risk (MP HR) or low risk (MP LR) per their MP results. We then grouped patients with discordant clinical and molecular risk. We then examined clinical features and NAC receipt amongst these clinical and molecular risk groups. Conclusions: There was discordance between clinical and molecular risk in 38% of our cohort, 20% were cLR/MP and 18% were cHR/MP LR. The decision to give NAC was primarily driven by clinical risk as only 1 patient with cLR/MP HR received NAC. Amongst cHR/MP LR 87% did not get NAC, but this appears to have been a clinical decision as only 7 of these patients had a pre-operative oncology visit at which MP/BP was mentioned. Most (72%) of > cN1 patients received NAC, of the 5 who didn’t, 4 were in the MP LR group and had a pre-operative oncology visit where MP was mentioned. In this select group the genomic assay may have influenced the decision to withhold NAC. Reflex genomic assays for HR+ HER2- breast cancer may not be useful; the decision to integrate molecular risk into the decision for NAC is multifactorial and stage of disease may be most impactful. Further work is needed in this area. [Table: see text] [Table: see text]