Among patients with the Kasabach-Merritt phenomenon (KMP) of kaposiform hemangioendothelioma (KHE), adding prednisone to sirolimus appears to improve outcomes compared with sirolimus alone, according to clinical trial data published in Blood.

KHE, a rare vascular cancer, is characterized by locally aggressive disease. As many as 70% of patients with KHE experience KMP, a thrombocytopenia and consumptive coagulopathy that can be life-threatening.

Clinicians aim to reduce the risk of bleeding in KMP by improving patient hematologic parameters. There is, however, no currently approved therapy in this setting in the United States.

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Previous research has shown that sirolimus may be effective among patients with KHE and KMP, and further that adding a corticosteroid may overcome treatment resistance. For this randomized study, researchers evaluated whether adding prednisone to sirolimus improves outcomes vs sirolimus alone among patients with KHE and KMP. The primary study outcome was durable platelet response (platelet count greater than 100 × 109/L at 4 weeks).

Overall, 73 people were enrolled and treated in this study. In the sirolimus and prednisone vs sirolimus group, 37 vs 36 patients were enrolled, respectively, 45.9% vs 50% were female sex, the mean age at discovery of tumor lesion was 1.5 vs 1.7 months, and the mean age at KMP onset was 2.1 vs 2.0 months.

At 4 weeks, 35 of 37 patients in the prednisone group vs 24 of 36 patients in the sirolimus only group reached the primary study endpoint (difference, 27.9%; 95% CI, 10-44.7). Patients in the prednisone group improved in measurable platelet response at all timepoints. These patients were also more likely to have a good lesion response (odds ratio, 3.061; 95% CI, 1.064-8.804).

Serious adverse events occurred in 11 patients in the combination group vs 10 patients in the sirolimus only group.

“Our study provided additional evidence for the use of sirolimus plus prednisolone in KMP patients not only to normalize hematologic parameters and reduce lesion mass promptly, but also to prevent long-term sequelae,” the authors wrote. “This work provides the foundation for future studies of sirolimus plus corticosteroids as a potentially effective oral treatment option for patients with active KMP.”


Ji Y, Chen S, Zhou J, et al. Sirolimus plus prednisolone vs sirolimus monotherapy for kaposiform hemangioendothelioma: a randomized clinical trial. Blood. 2022;139(11):1619-1630. doi:10.1182/blood.2021014027