P-1242. Beta-Lactam Therapeutic Drug Monitoring in the Hematology/Oncology Population

Abstract Background Beta-lactam pharmacokinetics can be significantly altered in patients with malignancy. Therapeutic drug monitoring (TDM; i.e., drug level testing) may facilitate pharmacokinetic/pharmacodynamic (PK/PD) target attainment, but the data are limited. This study aimed to characterize PK/PD target attainment of anti-pseudomonal beta-lactams in hematology/oncology patients.Table 1:Case DescriptionGraph 1:Distribution of Beta-Lactam TDM Indications Methods We conducted a retrospective review of beta-lactam TDM performed between June 2022 and June 2024 in hospitalized adults with hematologic or solid organ malignancies. We included patients who underwent beta-lactam TDM during clinical care, typically for extracorporeal membrane oxygenation (ECMO), extremes of body weight, suspected augmented renal clearance, multidrug-resistant infection, or suspected dose-dependent beta-lactam toxicity. Primary outcomes were (1) the proportion achieving target beta-lactam concentrations and (2) the proportion undergoing antibiotic dose adjustment based on TDM results.Table 2:Institutional Dosing Guidelines Results There were 47 TDM episodes in 20 unique patients. Considering only the first TDM per patient, 10 (50%) patients achieved target concentrations, 2 (10%) were below target, and 6 (30%) were above target. Antibiotic dose adjustments were made in 8 (40%) patients in response to TDM results. The most common indication for beta-lactam TDM was concerns regarding accurate renal clearance, followed by extremes of weight. Conclusion Retrospective findings suggest that beta-lactam TDM facilitated individualization of therapy in 40% of patients with either hematological or solid organ malignancy, with dose adjustments often intended to improve antibiotic safety. Future studies should refine the criteria for beta-lactam TDM use in this population and determine the need for tailored PK/PD targets in patients with impaired host response to infection. Disclosures All Authors: No reported disclosures