Introduction of an immunotherapy stewardship program at a single VA medical center.

81 Background: Pembrolizumab was approved by the FDA in 2014 at a dose of 2 mg/kg every 3 weeks (Q3W). The FDA-labeled dose was changed to 200 mg Q3W in 2017, and 400 mg Q6W was added in 2020. Despite these changes, fixed dosing has not proven superior to weight-based dosing, and retrospective evaluations strongly suggest equivalence between strategies. For clinical, logistical, and financial reasons, we launched a collaborative immunotherapy stewardship program. Efforts were focused on implementing dose-banded pembrolizumab and increasing Q6W adoption. Methods: The program began on July 1, 2024. It consisted of dedicated education sessions on pembrolizumab dosing for hematology/oncology fellows, quarterly reminders and educational updates for attending oncologists, and modifications to chemotherapy order templates incorporating dose bands that stratified patients by weight to provide the smallest whole-vial dose that exceeds the weight-based dose (Table). Dose selection was audited quarterly, and barriers to adoption were solicited during quarterly meetings with attending oncologists and team members. Outcomes of interest were pembrolizumab vial utilization, Q6W dosing adoption, and healthcare contact hours averted. Data cutoff was March 31, 2025. Results: In the program’s first 9 months, 63 unique patients received 286 total pembrolizumab doses, of which 107 (37.4%) were Q6W and 179 (62.6%) were Q3W. 741 total vials were utilized, which was a 5.7% reduction from the expected 786 vials. The program realized 86.5% of theoretical maximum savings. Q6W’s share of all doses rose from 27.3% in July 2024 to 53.8% in March 2025. Amongst monotherapy doses, Q6W’s share rose from 60.0% in July 2024 to 86.7% in March 2025. Using mean time of healthcare encounter (calculated post hoc as time from laboratory study collection to end of pembrolizumab infusion), Q6W adoption led to 381 patient-healthcare contact hours being averted, not including roundtrip travel time. Conclusions: This intervention demonstrates the potential of a collaborative stewardship program to reduce clinically redundant pembrolizumab administration, improve efficiency, and preserve patients’ time as well as facility resources. Future directions of the program include applying commonly accepted dose-rounding thresholds, extension of dose-banding to other immunotherapies, development of order templates combining Q3W chemotherapy dosing with Q6W pembrolizumab dosing, and regional expansion. Pembrolizumab dose bands in the immunotherapy stewardship program. Patient Weight Q3W Dosing Q6W Dosing < 50 kg 100 mg 200 mg 51-75 kg 200 mg 300 mg > 75 kg 200 mg 400 mg