e16521 Background: The costs of treating patients with metastatic breast cancer (mBC) have been examined in several studies, but there is very limited information regarding healthcare resource utilization (HCRU) and costs of mBC among Medicaid beneficiaries. The objective of this study was to characterize HCRU and costs in Medicaid among women with mBC. Methods: Women with mBC who were younger than 65 were identified using Thomson Reuters’ Medicaid claims data from 12-13 states (2005-2009). Overall HCRU and medical costs were estimated in those patients and compared to breast cancer (BC) patients without metastasis identified in the same population. Index date is the date of BC (or mBC) diagnosis and patients were followed to the date of disenrollment or the end of the study period, whichever occurred first. Mean (95% CI) cumulative healthcare costs were estimated using Kaplan-Meier Sample Average method. Results: 4,745 patients were included in the analysis. Among them, 3,767 were BC patients without metastasis and 978 with mBC. During an average of 14 months of follow up time, mBC patients on average incurred 1.56 hospital admissions, 9.01 inpatient days, and 1.97 emergency room (ER) visits, 25.54 physician office visits, 21.43 hospital outpatient visits, and 40.96 prescriptions. The total medical cost averaged at $63,068 (95% CI: $59,504, $66,624) per mBC patient, of which 33.0% were hospitalization costs, followed by hospital outpatient cost (27.4%) and physician office visit cost (14.8%). The average follow up time for BC patients was 18 months, during which BC patients on average incurred 0.69 hospital admissions, 3.79 inpatient days, 1.96 ER visits, 19.96 physician office visits, 12.27 hospital outpatient visits, and 40.89 prescriptions, and the total cost averaged at $29,776 (95% CI: $28,795, $30,762). Major cost drivers by type of service are similar to mBC. Conclusions: Overall HCRU and costs are substantially higher in mBC patients compared to BC patients of earlier stages in the Medicaid population, and the major cost drivers are similar in mBC and BC. Continuous Medicaid coverage is essential for BC/mBC patients in financial disadvantage to have access to quality medical care.