Operational and clinical drivers of subcutaneous PD-1/PD-L1 inhibitor adoption: A mixed-methods analysis of U.S. oncology practice patterns.

1550 Background: Subcutaneous (SC) formulations of PD-1/PD-L1 inhibitors have recently been approved across multiple solid tumors. While these agents offer operational and patient-centric advantages, their perceived clinical value relative to established intravenous (IV) formulations remains unclear. Understanding real-world oncologist perceptions may inform future adoption patterns and practice impact. Methods: A national mixed-methods study surveyed 102 U.S. hematologist-oncologists from academic (44%, n=45) and community (56%, n =57) practices across all U.S. regions (Nov- Dec 2025). A structured online questionnaire assessed brand utilization, regimen sequencing, physician satisfaction, switching behavior, and perceived comparative benefit between pembrolizumab- and nivolumab-based therapies using Likert-type scales and utilization metrics. All participants met predefined patient volume and clinical practice criteria. Eight qualitative interviews explored drivers of brand choice, sequencing, and switching decisions. Results: Across tumor types, oncologists reported modest current use of SC PD-1/PD-L1 inhibitors, with incremental uptake expected over the next six months. SC formulations were viewed as convenience-enhancing rather than clinically transformative, with reduced chair time (75% reporting significant benefit), improved infusion center efficiency (68%), and better patient experience (70%) cited as key benefits. Approximately half of PD-1/PD-L1–eligible patients across NSCLC, melanoma, and RCC were considered suitable for SC administration. Perceived benefit was largely limited to monotherapy and maintenance settings, with limited added value in curative-intent or combination regimens where infusion time is driven by other agents. In NSCLC, projected near-term uptake of SC PD-1/PD-L1 therapy was highest among PD-L1–high patients receiving monotherapy, while in melanoma and RCC, SC was more often positioned later in the treatment sequence, particularly after treatment stability. Insurance coverage (39% reporting a significant barrier) and cost (58%) were the primary barriers to broader adoption, outweighing concerns about safety (22%) or efficacy (27%). Overall uptake was expected to primarily substitute for IV monotherapy rather than expand total PD-1/PD-L1 use. Conclusions: U.S. oncologists view SC PD-1/PD-L1 inhibitors as operational alternatives to IV therapy, with adoption driven by efficiency and patient convenience and constrained by payer dynamics. SC administration is best positioned to enhance care delivery in monotherapy and maintenance settings, with limited incremental value in curative-intent or combination regimens. Addressing real-world access barriers will be key to broader integration across solid tumors.