Pioneering Safer Treatments: Low-Dose Sirolimus in Infantile Kaposiform Hemangioendothelioma

Background: Kaposiform hemangioendothelioma(KHE) is a rare and aggressive vascular neoplasm. When complicated with Kasabach-Merritt phenomenon, the condition is critical with a high mortality rate. Sirolimus (0.8 mg/m² per administration) exerts a significant therapeutic effect; however, under this conventional dosage, it is prone to induce various infections, immunosuppression and other adverse complications. This research aims to explore the efficacy and safety of low-dose sirolimus in the treatment of infants with KHE. Methods: A retrospective analysis was conducted on the treatment status of 7 infants with KHE who were treated with a low-dose stepped administration of sirolimus in our department from December 2021 to August 2024. For cases without Kasabach-Merritt phenomenon (KMP), sirolimus was used alone, and the doses were increased according to the age in months (for infants aged 1 - 3 months, 3 - 6 months, and 6 - 12 months, the initial doses were 0.1 mg/m²/time, 0.2 mg/m²/time, and 0.5 mg/m²/time respectively, all administered twice a day). For cases combined with KMP, glucocorticoid therapy was incorporated. The degree of tumor regression, hematological indexes and complications after treatment were summarized. Results: The duration of medication was from 7 months to 15 months, and the follow-up time was from 6 months to 2 years and 8 months. Among them, 2 had no KMP and 5 had KMP. For children without KMP, 1 case showed mostly regression, another had partial regression, with no adverse reactions. The 5 patients with KMP, the average time for the four indicators to return to normal was hemoglobin (26.8 ± 16.6) days, platelets (9.2 ± 3.9) days, fibrinogen (20.2 ± 15.8) days, and D-dimer (11.0 ± 10.2) days. Of these 1 case achieved complete regression, 3 cases had mostly regressed, and 1 case had partial regression. No obvious adverse reactions or recurrences were observed. Conclusion: Low-dose sirolimus is still significantly effective in the treatment of KHE in infancy. It has lower adverse reactions and higher safety. Furthermore, for cases combined with KMP, glucocorticoid therapy needs to be combined.