Informing optimal treatment (tx) sequences for platinum-eligible patients with locally advanced or metastatic urothelial carcinoma (la/mUC) in the United States: Results of a clinical simulation modeling exercise.

e13514 Background: Platinum-based chemotherapy (PBT) followed by avelumab (AVE) as first-line (1L) maintenance for patients with nonprogressive disease (PBT ± AVE) is the standard of care in la/mUC. This study compared the overall survival (OS) and cost-effectiveness of the tx sequence of PBT ± AVE followed by enfortumab vedotin (EV) or other therapies, including immuno-oncology (IO), in second line (2L; ie, PBT + 2L EV/IO or PBT + AVE + 2L EV/IO) vs 1L EV + pembrolizumab (PEM) for PBT-eligible patients (PBTp) from a US commercial payer perspective. Methods: A partitioned survival model compared outcomes with PBT ± AVE and EV + PEM among PBTp. Inputs included progression-free survival and OS, time to tx discontinuation, adverse event (AE) incidence, and health utilities and costs. Efficacy inputs were sourced and extrapolated from patient data in JAVELIN Bladder 100 (data cut: Jun 4, 2021), AVENANCE real-world study (1), and published data (EV-302 trial). Safety data were sourced from US prescribing information. Drug, subsequent tx, disease management, and AE management costs (2023 USD) were calculated. The optimal tx sequencing scenario assumed 80% of patients starting PBT were eligible to receive AVE (2023 Flatiron data cut; (2) ), 70% of patients progressing on PBT ± AVE would start 2L, and 70% of those would be eligible for EV. Outcomes included life-years (LYs), quality-adjusted LYs (QALYs), costs, and incremental cost-effectiveness ratio (ICER). Scenarios and probabilistic sensitivity analyses (PSAs) were conducted to assess uncertainty. Results: LY, QALY, costs, and ICER modeling outcomes are shown in the Table. Use of EV in 2L after PBT ± AVE is associated with 0. 76 lower QALYs, but given the large cost saving, it represents a cost-effective use of resources at the 150, 000/QALY willingness to pay (WTP) threshold. PSAs showed that PBT ± AVE is likely to be more cost-effective over a broad and relevant WTP threshold range (0-500, 000/QALY). Results were sensitive to drug acquisition costs and eligibility to receive AVE and 2L EV. Conclusions: Based on this simulation exercise, the use of 2L EV after PBT ± AVE achieves considerable survival benefit at substantially lower costs vs 1L EV + PEM in PBTp with la/mUC. Given the shift toward value-based care in oncology, such analyses are becoming increasingly relevant to guide clinical decision-making. There is a need to assess tx alternatives that balance healthcare costs while optimizing outcomes in patients with la/mUC. 1. Barthélémy et al, J Clin Oncol 2024;42suppl 4: Abstract 561. 2. Moon et al, J Clin Oncol 2023;41suppl 16: Abstract 4567. Table: see text