Early adoption of lecanemab in Japan (December 2023–December 2024): Pretreatment diagnostic timelines from the DeSC claims database

Using the Japanese DeSC claims database, we described pretreatment timelines for lecanemab initiation during early rollout (December 2023–December 2024). We identified 76 patients (mean age 74.6 years; 34.2% men) from 45 institutions. Mean time to first infusion was 103.9 days from cognitive assessment and 63.1 days from MRI. PET-to-infusion was 30.9 days, whereas cerebrospinal fluid (CSF) sampling-to-infusion was 85.8 days; the post-test interval remained longer after CSF (Bonferroni-adjusted p = 0.015). Although this claims-based snapshot may not represent all practice in Japan, it suggests that the CSF-based pathway can be associated with a longer post-test interval before treatment initiation.