Abstract P1-02-12: Genomic testing on breast cancer core biopsy material is feasible and provides useful treatment information
Authors: Gilmore Hannah , Bomeisl Philip , Montero Alberto 
Published: March 2022

Background: Genomic profiling assays for invasive breast cancer provide useful predictive and prognostic information and are performed most commonly on surgical resection specimens. Obtaining the molecular profile at the time of initial core needle biopsy is ideal because it could provide information that could significantly alter preoperative decision-making and avoid unnecessary treatments. In January 2020, the breast center began a 3 month pilot program that would reflexively send core biopsy material on all newly diagnosed patients for genomic testing using the MammaPrint (MPT) and BluePrint (BPT) assays regardless of receptor status. The goals were to determine feasibility and examine the impact to patient care. Methods: Breast core biopsy tissue was triaged by an attending pathologist as soon as slides were available. If invasive carcinoma with at least 3 mm in linear extent of tumor with 20% cellularity was identified, materials were immediately sent to Agendia for MPT/BPT testing even before ER/PR/HER2 testing was available to the pathologist. Clinicopathologic information, turn-around time (TAT) and adequacy data were tracked. The impact was discussed regularly at breast tumor board to determine if the results led to altered decision-making that could reduce unnecessary interventions and time to initial treatment. Results: 445 core biopsy specimens were sent for genomic testing. Of those 442, (97%) yielded genomic results with an average TAT from biopsy to genomic result of 11 calendar days. MPT identified 233 (53%) cases that were low risk and 209 (47%) cases that were high risk. BPT showed that 60 (14%) cases were Basal, 18 (4%) cases were HER2, and 364 (82%) cases were Luminal. Further analysis of the Luminal subgroup demonstrated that 154 (42%) were Luminal A low risk, 78 (21%) were Luminal A Ultralow risk and 132 (36%) were Luminal B High Risk. Analysis by race demonstrated a significantly higher percentage of high risk tumors in African-American women including a higher percentage of basal cancers (26%) as compared to Caucasian women (10%). Of note, 51 patients in the pilot study had additional OncotypeDX (ODX) testing on subsequent surgical resection. There was fair correlation between the assays with the majority of the low risk MPT having low risk ODX scores (&lt;=25) and the high risk MPT having high risk ODX scores (&gt;25), though MPT identified more patients as being high risk. The COVID-19 pandemic altered plans to assess time to treat and treatment interventions as initially intended. However, the knowledge of genomic result enhanced the ability to triage patients, allowing those patients with low risk tumors to begin endocrine therapy and delay surgery. Use of preoperative hormone therapy was considered more often in place of neoadjuvant chemotherapy in patients with low genomic risk ER+/HER2- patients. Because of the continued feedback indicating positive impact, the pilot ultimately was extended to 11 months to allow time for formal implementation. Conclusions: Genomic testing using the MPT/BPT assay on core biopsy samples with at least 3 mm yields results 97% of the time with an average TAT of 11 days from biopsy date to result. The genomic information at the time of initial diagnosis impacted patient care most notably in the ER+ setting. The results led to the immediate implementation of direct reflex testing of all newly diagnosed ER+ and HER2- or IHC 2+ cancers by pathology after the initial pilot phase.

Citation Format: Hannah Gilmore, Philip Bomeisl, Alberto Montero. Genomic testing on breast cancer core biopsy material is feasible and provides useful treatment information [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-02-12.