Systemic Sirolimus Monitoring in Pediatric Pulmonary Vein Stenosis

Systemic sirolimus (SS) is an mTOR inhibitor used in the management of pediatric intraluminal pulmonary vein stenosis (PVS). SS initiation, monitoring, including patient compliance with toxicity surveillance, and potential adverse events (AE) in PVS patients are under reported. A single-center retrospective cohort study of consecutive patients who were initiated on SS for PVS from January 1, 2020 to December 31, 2024 was performed. Fifty patients with a median age of 7 months (range 2-165) received SS for PVS (median number of stenotic veins; n = 3 (1-4)) for a median duration of 18 months (1-60). The median time to therapeutic level was 9 days [IQR 3, 20] with two never achieving therapeutic values. In patients who received SS for at least 6 months (n = 39), the median number of blood draws and number of dose adjustments in the first 6 months were 14 [IQR 5, 27] and 3 [1, 7], respectively. Most levels among patients (75%; [IQR 64, 84]) did not require a dose adjustment. Toxicity surveillance compliance increased from 58% [IQR 42, 83] to 79% [IQR 62.5, 92] (p = 0.22) following transitioning ownership of SS management to a dedicated PVS team. Eighteen percent (9/50) of patients had an AE potentially related to SS; SS was discontinued in three. PVS patients receiving SS have high, but variable rates of therapeutic levels and SS discontinuation due to AEs is uncommon. Compliance with safety labs may improve with ownership by a dedicated monitoring team.