Evaluation Of High-Dose Methotrexate Serum Concentration Requirement For Discharge.

e19204 Background: Methotrexate (MTX) is used in high doses for the treatment of ALL, lymphoma, and metastatic breast cancer with CNS involvement. To avoid drug accumulation and mitigate toxicities caused by delayed clearance, patients (pts) are usually admitted to the hospital and standard supportive care with IV hydration, urinary alkalization, and leucovorin is provided and adjusted based on daily levels. Historically, a serum methotrexate level ≤ 0.05 µmol/L has been used to declare clearance and an ideal level for discharge based on studies conducted in the 1970s. We conducted a retrospective review in 2018 to identify frequency of supportive dose escalations required with MTX levels > 0.05 µmol/L. In 69 pts, 4 patients demonstrated delayed renal clearance and required supportive care escalations but all occurred at MTX levels > 0.3 µmol/L. This led to a proposed pilot discharge process once MTX was < 0.3 µmol/L to confirm the safety of earlier discharge. Methods: A retrospective chart review of pts with baseline CrCl ≥60 who received HD MTX between 07/2018 – 08/2019. Data collection included diagnosis, MTX discharge level, supportive care at discharge including PO Leucovorin and PO sodium bicarbonate and number of days supply, post-discharge complications (AKI, mucositis, fever, others). Primary outcome was the number of patients who required inpatient or outpatient supportive care for acute complications after being discharged with a methotrexate level ≥ 0.1 µmol/L. Descriptive statistics were used. Results: A total of 41 pts were included. Median age was 55 yrs (32-78), 25% were male. 73% were treated for DLBCL, median dose of MTX was 3500 mg/m2. Median MTX level at the time of discharge was 0.16 µmol/L (0.1-0.3 µmol/L). 12 pts were discharged with PO Leucovorin and 15 pts were discharged with both Leucovorin and PO Sodium bicarbonate with an average of 2 day’s supply. 1 acute complication of neutropenic fever requiring admission for inpatient antibiotics occurred which was felt to be unrelated to MTX level at discharge. Conclusions: This pilot suggests that pts can be safely discharged with MTX levels upto 0.3 µmol/L without acute complications. Results of this study will be used to a develop a standardized protocol outlining criteria for early discharge in select pts with MTX levels < 0.3 µmol/L to reduce length of stay, cost of hospitalization and improve patient satisfaction. [Table: see text]