Background: Oncology care, including drugs, represents a significant portion of US healthcare spending. Cost of Part B drugs has increased at a rate 5.7x that of overall Medicare spending (1997-2004). As a participant in the Oncology Care Model (OCM), we found drug costs represent a majority of our total costs. To reduce treatment (Tx) variability, our NCI-designated cancer center chose to implement pathways. Pathways are a clinical decision-support tool that use evidence-based care maps accounting for efficacy, toxicity and cost. At one institution, use of pathways contributed to $15k in savings for stage IV lung cancer Tx. We hypothesized pathway driven Tx standardization would favorably impact total chemotherapy (CTx) costs at the implementation site. Methods: In July 2018, we implemented pathways in Medical and Radiation Oncology for new starts or changes in Tx. Oncologists accessed the tool through our EMR, selected and placed orders for Tx. OCM quarterly data was used to compare 2 quarters immediately pre- and post-pathway implementation. The cancer-mix-adjusted Per-Member-Per-Month (PMPM) Allowed Amounts for CTx were compared between 3 groups; patients on-pathway, patients off-pathway and patients for which the pathways tool was not used (no utilization). PMPMs were evaluated pre- and post-implementation and an ANOVA test was used to evaluate significance of the difference between the two periods. Results: PMPM CTx costs decreased 4.6% between pre- and post-pathway implementation when oncologists followed pathways. By comparison, the off-pathway cohort and the no utilization groups had increases of 0.9% and 17.7% respectively. An evaluation of cost difference proved significant (p < .0001). Breast patients on-pathway had a cost decrease of 20%, compared to increases of 32% and 11% for off-pathway and no utilization groups, respectively. Conclusions: Pathway use reduced variation, a known contributor to healthcare costs, and therefore may be an effective cost control tool. Additional quarters of claims data is needed post-implementation to fully define the impact of pathways on total cost.