BACKGROUND: A recent study demonstrating the use of Therapeutic Drug Monitoring (TDM) in patients with chronic myeloid leukemia (CML) resulted in a higher response rate with imatinib (IM) than demonstrated in second-generation tyrosine kinase inhibitor studies. The cost-effectiveness of TDM combined with IM (IM TDM) in first-line CML treatment has not yet been studied. OBJECTIVES: To determine the cost-effectiveness of IM TDM for the first-line treatment of CML compared to tyrosine kinase inhibitor only treatment. METHODS: A recently published cost-effectiveness model of tyrosine kinase inhibitor-treatment in CML was modified to include IM TDM as a first-line tyrosine kinase inhibitor-based CML treatment option. Efficacy inputs for major molecular response (MMR) rates were taken from previously published studies: IM TDM 65%, dasatinib 52%, nilotinib 53%. Annual tyrosine kinase inhibitor drug prices were derived from the Federal Supply Schedule (FSS) and the average and lowest wholesale acquisition costs (WAC) reported in the Red Book; the annual cost of TDM was $228. Other input costs modeled in the original CML CEA model were updated to 2016 US dollars using the medical service component of the Consumer Price Index. A US payer perspective was used with a 5-year time horizon and a 3.0% discount rate. The model compared first-line IM TDM versus IM alone, nilotinib (NIL) or dasatinib (DAS) in terms of the following outcomes: costs, quality-adjusted life-years (QALYs), and cost-effectiveness (total cost/QALY). Deterministic and probabilistic sensitivity analyses were performed using all key clinical and economic parameters. RESULTS: This study found that IM TDM dominates IM alone with $15,452 to $36,940 in savings and 0.25 higher QALYs. Using FSS, per patient total costs for IM and IM TDM were $270,905 and $233,965, respectively.; Using average WAC, these costs were $461,657 and $446,205, and using lowest WAC, these costs were $366,966 and $350,090. The results comparing first line using of IM TDM to NIL/DAS found that TDM IM had higher QALYs and lower costs (0.08 QALYs lower, and $117,006 to $172,420 savings per patient [varying by price basis]). Thus, in terms of cost-effectiveness, IM TDM dominates NIL/DAS with both lower costs and higher QALYs. CONCLUSIONS: IM TDM is a clinically and economically viable first-line treatment option for CML. DISCLOSURES: This study was funded by Saladax Biomedical. Salamone is an employee of Saladax Biomedical. This study was presented at the IATDMCT Congress, September 2018, Brisbane, Australia.