Comparison of Discontinuation, Health Care Resource Utilization (HRU), and Costs Between Metastatic Breast Cancer (mbc) Patients (pts) Who Received Trastuzumab (T) in an Office Clinic Versus Outpatient Hospital Setting.

642 Background: T treatment for mBC may be administered in an office clinic or outpatient hospital setting. This study assesses the impact of the site of care on T discontinuation risk, HRU, and costs. Methods: Adult women with mBC who received ≥2 T infusions in an outpatient hospital or office clinic setting were selected from the US-based Humana database (2007-2012). Pts were required to be continuous eligible in their healthcare plan for ≥6 months prior and ≥2 months following the first T infusion (index date). Pts were classified, based on their index site of care, into one of the following cohorts: 1) office clinic, or 2) outpatient hospital. Outcomes were measured from the index date up to the end of continuous eligibility/data availability, a change in the site of care, or 12 months after the index date, whichever occurred first. Treatment discontinuation (gap ≥45 consecutive days) was compared between cohorts using multivariate Cox-proportional hazards model. Monthly healthcare costs (2012 USD) and HRU were compared between cohorts using multivariate generalized linear/two-part models, and multivariate negative binomial regression models, respectively. Results: A total of 280 pts met the inclusion criteria; 64% and 36% in the office clinic and outpatient hospital cohort, respectively. Baseline characteristics were similar between cohorts. However, differences were found in terms of insurance plan type, year of index date and comorbid conditions (chronic pulmonary disease and peripheral vascular disorder). After adjusting for confounding factors, the outpatient hospital cohort had a 1.5 time higher risk of treatment discontinuation (p=.043) and incurred an incremental monthly cost of $1,954 (p=