Characterization Of Bone Only Metastasis (Bom) Patients (Pts) With Respect To Tumor Subtypes (Ts).

1072Background: Metastatic breast cancer (MBC) pts with BOM are a unique population with limited characterization. Our goal was to characterize the TS of BOM pts, evaluating differences in sites and types of bone metastases (BM), treatment, and survival. Methods: We identified pts followed at MD Anderson Cancer Center from 01/01/1997 to 12/31/2015 for at least 6 months with a BOM diagnosis as first site of metastasis (met). TS was assessed by initial biopsy immunohistochemistry (IHC) (Table 1) with hormone receptor (HR) + defined as ER or PR u003e10%. Results: We identified 1445 pts with BOM, 1049 with initial biopsy IHC available to group into TS (Table 1). Among BOM pts, the majority had multiple BM at diagnosis (1141/79%), most in both the axial (Ax) and appendicular (App) skeleton (53%). Of the 808 pts with BM categorized on imaging at diagnosis, the majority were lytic (389/48%), with 21% sclerotic, 18% mixed, and 12% blastic. Time from breast cancer diagnosis to first met differed significantly by TS, χ...