Analysis Of Circulating Tumor Cells (Ctcs) In Patients Across Multiple Metastatic Breast Cancer (Mbca) Cohorts Identifies Marked Inter- And Intra-Patient Heterogeneity In Ctc Size, Shape, And Overall Morphology.

1084Background: The choice between hormonal therapies and chemotherapy is a frequent decision in the care of mBCa pts. We previously developed quantitative measures of phenotypic CTC heterogeneity in mCRPC, and found higher heterogeneity was associated with better survival on chemotherapy vs. targeted hormonal therapies, and the reverse was true in low heterogeneity patients (Scher et al. 2017 Cancer Research). We sought to apply our previous heterogeneity quantitation methodologies to a cohort of mBCa patient CTCs to ascertain feasibility in mBCa. Methods: 295 blood samples from mBCa patients were processed for CTC analysis utilizing the Epic Sciences platform. Following enumeration, multi-dimensional phenotypic characterization analysis was performed utilizing protein expression and digital pathology features. Features from each CTC (3994 CTCs from 165 pts, 84 HR+, 19 Her2+, 8 HR+/Her2+, 54 TNBC) were compared by unsupervised clustering, Shannon Index and intra-patient variance analyses to assess the in...