The Kasabach-Merritt phenomenon (KMP) is characterized by life-threatening thrombocytopenia and consumptive coagulopathy in kaposiform hemangioendothelioma (KHE). In the biggest cohort to date, researchers for a trial assessed the effectiveness and safety of sirolimus with prednisolone against sirolimus monotherapy as treatment regimens for KHE with KMP. For at least 12 months, participants were randomly assigned to either sirolimus in conjunction with a short course of prednisolone or sirolimus monotherapy. The primary goal was to achieve a long-term platelet response (platelet count >100 x109/L) by week 4. Two years following the initial therapy, participants underwent efficacy assessments. 

At week 4, 35 of 37 patients given sirolimus and prednisolone had a durable platelet response, compared to 24 of 36 patients given sirolimus alone (difference 27.9%; 95% CI, 10.0-44.7). The combination treatment group outperformed the sirolimus monotherapy group in terms of measures of durable platelet responses at all points during the initial 3-week treatment period, median platelet counts during weeks 1 to 4, increased numbers of patients achieving fibrinogen stabilization at week 4, and objective lesion responses at month 12. Combination treatment patients required fewer blood transfusions and had a lower overall incidence of disease sequelae than sirolimus alone individuals. During therapy, the incidences of total adverse events and grade 3-4 adverse events were comparable in both groups. 

The responses shown in patients with KHE with KMP were significant and encouraging, indicating that sirolimus with prednisolone should be regarded as a viable therapy option for KHE with KMP.