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.