Long-term outcomes of low-dose radiotherapy in Kasabach-Merritt syndrome

Purpose: Reports on results of radiation therapy (RT) for Kasabach-Merritt syndrome (KMS) are limited. We performed a retrospective study to evaluate the response rates and late complications and to determine the adequate RT dose for patients with KMS patients. Materials and Methods: We studied 11 patients who received RT between October 1988 and September 2008 for KMS refractory to pharmacologic therapy. All patients had external hemangiomas and received the diagnosis of KMS within 12 months of birth. All 11 patients received steroids as the first-line therapy; eight patients additionally received interferon-a therapy, and one patient underwent surgery. Nine patients underwent single-course RT with a total dose of 4.5-8 Gy (1.5-2 Gy/fraction). Two patients received multiple courses of RT, with a cumulative total dose of 12 Gy (2 Gy/fraction) and 18 Gy (1.5 Gy/fraction), respectively. Results: The median follow-up period was 156 months (interquartile range [IQR], 75 to 226 months). The median total dose of RT was 6 Gy, and all patients maintained complete remission until the last follow-up. An additional course of RT was performed for refractory cases or cases of local relapse after initial RT. Rapid platelet count increase after RT was seen in most patients, which returned to normalcy in a median of 20 days (IQR, 5 to 178 days). However, seven patients experienced radiation-related long-term complications. Conclusion: Low-dose RT is effective and yields rapid response in patients with KMS. However, given growth-related late complications, RT should be carefully considered.