The purpose of this study is to compare the efficacy and safety of different concentration gradients of sirolimus in the treatment of Kaposiform hemangioendothelioma.

Kaposiform hemangioendothelioma (KHE) is a rare aggressive vascular neoplasm that occurs predominantly in infancy or early childhood, with an incidence of approximately 0.71/100,000. Currently, sirolimus is a promising treatment modality for KHE. Most scholars consider sirolimus blood concentration of 5-15 ng/ml to be an effective therapeutic concentration.

However, long-term higher dose sirolimus treatment can cause some common complications such as oral mucositis which affects the quality of life of the patient. Finer control of the plasma concentration of sirolimus may contribute to the efficacy of treatment and reduce the incidence of complications. Therefore, we conducted this study to see if low-dose sirolimus is beneficial to the prognosis of patients.

Inclusion Criteria:

Presenting a KHE with the following characteristics:

1. Male and female;

2. Between 0 and 14 years of age;

3. KHE diagnosis was confirmed by local investigators and by consensus of our multidisciplinary vascular anomaly group at the West China Hospital of Sichuan University based on:

   • Biopsy;
   • Compatible MRI findings;
   • History and clinical features.

   The multidisciplinary vascular anomaly group was a collaboration team that included vascular anomaly experts in pediatric surgery, plastic surgery, pediatric dermatology, pathology and radiology.

4. Without KMP, which was defined as a platelet count of less than 100×10^9/L, with consumptive coagulopathy and hypofibrinogenemia.

5. Patients were required to have adequate liver, renal and bone marrow function, and absence of active infection

6. Consent of parents (or the person with parental authority in families): signed and dated written informed consent.

Exclusion Criteria:

1. Patients contraindicated for the administration of sirolimus (e.g., those with an allergy to sirolimus or other rapamycin analog)

2. Exposure to chemotherapy, embolization, corticosteroids, propranolol, sclerotherapy or any other investigational agents within 1 weeks before enrolment on study;

3. Patients had a history of a major surgery within 2 weeks before enrollment;

4. Patients who have a history of treatment with sirolimus or other mTOR inhibitor;

5. Any known evidence of significant local or systemic uncontrolled infection, defined as receiving intravenous antibiotics at the time of enrollment;

6. Concurrent severe and/or uncontrolled medical diseases that could compromise participation in the study (e.g. uncontrolled diabetes, uncontrolled hypertension, severe malnutrition, chronic liver or renal disease, active upper gastrointestinal tract ulceration).

7. Impairment of gastrointestinal function or chronic gastrointestinal disease that may significantly alter the absorption of sirolimus.

8. Patients with inadequate liver function:

   Total bilirubin higher than or equal to 1.5 × the upper limit of the normal (ULN) for age and alanine aminotransferase and aspartate aminotransferase higher than or equal to 2.5 × the ULN for age.

9. Patients with inadequate renal function:

   0-5 years of age maximum serum creatinine (mg/dL) of 0.8; 6-10 years of age maximum serum creatinine (mg/dL) of 1.0; 11-14 years of age maximum serum creatinine (mg/dL) of 1.2;

10. Adequate bone marrow function:

    Absolute neutrophil count lower than 1 × 109/L;

11. History of a malignancy within 5 years;

12. HIV infection or known immunodeficiency;

13. Indication for treatment with corticosteroids, vincristine, interferon-α, sirolimus, or tacrolimus for an indication other than IH;

14. Patients with an inability to participate in or follow-up during the study treatment and assessment plan;

15. Inability to give informed consent.