Clinical and molecular characterization of a cohort with breast cancer brain metastases.

Abstract

e13122 Background: Breast cancer (BC) is the most common cancer in Women in the United States, it is the second most frequent cause of brain metastases (BM). Despite steady improvement in BC treatment (tx) and prognosis, BM continues to be an unmet need. With most BM patients excluded from clinical trials, the study of cohorts remains an important source of information regarding this aspect of the disease. We aim to characterize incidence, disease course, tx, and molecular profile of BM for BC subtypes. Methods: In this single-center retrospective analysis, we identified all adult patients (>18 years) diagnosed (dx) with BC as well as secondary malignant neoplasm of the brain from 1/1/15 to 10/1/22 using database query from EMR. Baseline characteristics were obtained through chart review. Molecular profiling was performed in a total of 41 patients, 8 of which was from brain tissue. Next generation sequencing (NGS) was the most used method. Results were generated using descriptive statistics. Results: We identified 304 BC patients with BM (median age = 60 years [range: 24 to 88]). Baseline characteristics are described in table 1. Hormone receptor positive/HER2-neu negative (HR+/HER2-) was the most commonly observed BC subtype (41.4%), and triple negative BC (TNBC) was the least frequent (16.8%). On primary tissue biopsy, five patients with recurrent BC had a subtype shift that differed from their initial disease: 2 patients with HR +/HER2 – BC subtype recurred with TNBC, 2 patients with a HR+/HER2- recurred with HR+/HER2+ BC, and 1 patient with TNBC at initial dx had their disease shift to HR+/HER 2- BC at first metastatic recurrence then back to TNBC 4 years after initial dx. NGS was available for 41 patients, with TP53, MSS, PIK3CA and ERBB2 being the most frequently observed mutations. On average, 3 lines of therapy were used before dx of BM. In the metastatic setting, capecitabine was one the most commonly used drugs. Targeted central nervous system (CNS) tx used in this study population include WBRT, SRS, SBRT and surgical resection. Conclusions: Studying patterns of disease presentation, progression during standard tx, and the molecular characteristics accompanying BM will enable us to develop more effective tx for patients. Our cohort includes a spectrum of BC subtypes and natural histories. Further characterization of this cohort with tx interactions, progression and survival timeline is ongoing and will be reported at the meeting. [Table: see text]