A retrospective, descriptive analysis of a single-center experience with patients with metaplastic breast cancer.

e13173 Background: Metaplastic breast cancer (MpBC) is a subtype of breast cancer (BC) that is commonly triple negative (TN) and chemotherapy (CT) resistant. Despite CT resistance, standard of care therapy is administered according to receptor status, regardless of metaplastic histology. Randomized data regarding optimal treatment of this rare histologic subtype are lacking. Methods: This was a retrospective analysis of MpBC patients (pts) treated at Miami Cancer Institute (MCI) between 2017 and 2021. Pts were identified using COTA real-world Analytics, an analytics platform enabling rapid investigation of longitudinal real-world data. Pt demographics, pathologic characteristics, staging, treatment, and survival outcomes were collected and analyzed. Results: 46 pts with MpBC were identified. Median age at diagnosis was 60.5 years, and 83.7% were post-menopausal. 84.8% were White, 10.9% were Black, and 54.3% were Hispanic (all White). 80.4% (n=37) had TNBC (ER 80%). Our dataset represents the largest cohort to date of Hispanic pts with MpBC. Despite the poor outcomes historically reported with MpBC, median DRFS and OS were not reached in this cohort, with short follow up. Further prospective randomized data on the optimal treatment of MpBC is warranted and a larger multi-institution review is planned.