Sirolimus Early Treatment in Vascular Anomalies Leads to a Better Response

Objectives: Sirolimus has become a relevant drug in the treatment of vascular anomalies, initially relegated to rescue therapy for refractory lesions but more recently has become first line. Our objective is to determine when it is best to start sirolimus treatment. Methods: A retrospective review of patients with vascular anomalies treated with sirolimus during a 9-year period was performed. The variables analyzed included subtype of vascular anomaly, age at the start of treatment, sirolimus dosage and levels, response, and duration of treatment among others. Results: One hundred twenty-two patients were included and classified according to ISSVA in: tumor (7), lymphatic malformation (60), venous malformation (16), combined malformations (18), associated overgrowth (8), and others (15). Overall response was positive in 90.8%. Median duration of treatment was 32 months (0–116). Response was not influenced by dosage or levels, neither by the subtype of vascular anomaly, location, extension, symptoms, genetic testing nor previous treatments. However, the lower the age of starting sirolimus, the better the response, mainly under 5 years of age ( P = 0.004). At 6 months, 67% of patients had responded while at 12 months >84% did. By age, patients <5 years showed positive response at a median time of 2 months, compared to >5 months from older patients. Time until a positive response was not influenced by subtype or severity. Conclusion: Overall response to sirolimus was good and most patients responded irrespective of their severity in location, extension or symptoms. Patients <5 years old respond better and faster making our goal to attempt for an early treatment.