17082 Background: mTC is relatively rare and little is known about treatment patterns or HC costs in patients with newly diagnosed disease. Methods: Retrospective longitudinal cohort study. Using a large (∼14 million covered lives) US health-insurance claims database, we identified a cohort of pts with diagnoses of thyroid cancer (ICD-9-CM diagnosis codes 193.XX) and distant metastatic disease (197.XX-198.XX) between 1/1/2003 and 12/31/2005 (“study period”); the date of first mention of metastatic disease was designated the “index date”. All pts were required to be =18 years of age as of their index date and to have been continuously enrolled in the database for =6 months prior to this date. Pts were followed from their index date until health plan disenrollment (for any reason) or end of the study period, whichever occurred first. Utilization of HC services and costs (total reimbursed amount including pt liability) were then examined during each quarter of follow-up (eg, first 3 months of follow-up=Q1). Results: 183 pts met all study entry criteria. Mean (±SD) age was 51.5 (11.8) years; mean duration of follow-up was 344 days (median=275 days). Most common management/treatment strategies during Q1 included: imaging [eg, US/CT of the neck (49.7%)], thyroglobulin/thyroglobulin antibody testing (25.7%); radiation therapy (23.0%); I131 therapy (19.1%); thyroid surgery (12.6%); chemotherapy (10.9%); lymphadenectomy (8.7%); and bisphosphonate therapy (3.8%). In addition, during Q1, pts averaged 9.5 office visits (95% CI, 8.2, 10.9) and 0.6 hospitalizations (95% CI, 0.5, 0.7); for pts hospitalized during Q1, average length of stay was 6.6 (95% CI, 4.9, 8.4). Costs during the first 2 years of follow-up are presented in the table ; inpt care represented 43% of total HC costs. Conclusions: Many different treatment modalities are used in pts with newly diagnosed mTC; the cost of such care is substantial. [Table: see text] [Table: see text]