Sirolimus Versus Sirolimus Plus Prednisolone for Kaposiform Hemangioendothelioma

Overview

Kaposiform hemangioendothelioma (KHE) is a rare vascular neoplasm that occurs predominantly in infancy or early childhood. KHE has a nearly equal sex ratio. The annual incidence of KHE has been estimated at 0.071 per 100,000 children. KHE presents with intermediate-malignant and locally aggressive characteristics but without distant metastases. This pilot trial studies sirolimus versus sirolimus plus pednisolone in treating patients diagnosed with kaposiform hemangioendothelioma (KHE) and Kasabach-Merritt phenomemon (KMP) that cannot be removed by surgery. The purpose of this study is to compare the efficacy and safety of orally administered sirolimus versus sirolimus plus pednisolone in the treatment of KHE associated with KMP.

Kasabach-Merritt phenomemon (KMP) is a profound thrombocytopenia resulting from intralesional platelet trapping. It is now clear that KMP occurs with KHE and tufted angioma, not with infantile or congenital hemangiomas. KMP is typically associated with more aggressive lesions and poorer outcomes. Clinically significant KMP is a severe thrombocytopenia, generally below 30× 109/L. Severe thrombocytopenia may indicate a severer tumor, a progressive tumor, partially or totally insensitive to therapy. In addition to severe, persistent thrombocytopenia characteristic of KMP, patients often manifest elevated D-dimer and low fibrinogen. Coagulopathy in addition to thrombocytopenia is associated with more aggressive presentations and may indicate current infection or inflammation. Additionally, KMP may be complicated by severe anemia due to blood sequestration and intra-lesional hemorrhaging. KHE with KMP have notably high morbidity and mortality rates, resulting predominantly from rapid tumor growth and infiltration, compression or destruction of vital structures, and hemodynamic instability. Consensus treatment guidelines from a multidisciplinary expert panel were published in 2013. Medical treatments with corticosteroids and/or vincristine have been recommended for the management of KHE. However, first-line treatment with corticosteroids is successful in only 10-27% of all cases, and treatment with vincristine is successful in 60-70% of patients. Moreover, vincristine monotherapy has not been confirmed to provide significant benefits in critically ill patients. Sirolimus (also known as rapamycin) is an inhibitor of the mammalian target of rapamycin (mTOR). In recent studies, sirolimus was shown to be effective in patients with complex vascular anomalies, including KHE. Our multicenter, retrospective study demonstrated that oral sirolimus is an effective and safe option for the treatment of progressive KHE. Additionally, our data emphasized that the KHE treatment regimen should be tailored to individual patients and guided by specific clinical circumstances. In cases of severe Kasabach-Merritt phenomenon (KMP), sirolimus in combination with the short-term administration of prednisolone is recommended for controlling life-threatening conditions.