Methods
We performed a retrospective chart review from September 2019 to April 2020 at two European Reference Centers for Vascular Anomalies (Freiburg/Germany, and Rome/Italy), three national referral centers for Vascular Anomalies (Barcelona/Spain, Montpellier/France and Bern/Switzerland) and two German Pediatric Oncology units (Köln and Ulm) to identify patients treated with sirolimus that developed an SAE. Medical history of the identified patients were analyzed using a pre-designed algorithm. Definition of SAE was according to Good Clinical Practice (GCP) rules and included any event that resulted in death, was life-threatening, required inpatient hospitalization or caused prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, might have caused a congenital anomaly/birth defect, or required intervention to prevent permanent impairment or damage. The treating physician had received patient/parental informed consent before transferring data for the study. This study is covered by the ethical committee numbers Freiburg 310/14 and 464/19.