Background and Objectives: Kaposiform hemangioendothelioma (KHE) and tufted angioma (TA) are rare vascular tumors in children historically associated with significant morbidity and mortality. This study was conducted to determine first line therapy in the absence of available prospective clinical trials. Methods: Patients from 17 institutions diagnosed with KHE/TA between 2005-2020 with > 6 months follow-up were included. Response rates to sirolimus and vincristine were compared at 3 and 6 months. Durability of response and response to other treatment modalities were also evaluated. Results: Of 159 unique KHE/TA subjects, Kasabach-Merritt phenomenon (KMP) was present in 64 (40.3%) and only 2 patients were deceased (1.3%). Over 60% (n=96) demonstrated treatment response at 3 months and >70% (n=114) by 6 months (no significant difference across groups). The vincristine group had higher radiologic response at 3 months compared to sirolimus (72.7% vs 20%, p=0.03) but there was no differences between these groups at 6 months. There were no differences in rates of recurrent or progressive disease between vincristine and sirolimus. Conclusions: In this large, multicenter cohort of 159 patients with KHE/TA, rates of KMP were consistent with historical literature but the mortality rate (1.3%) was much lower. Overall treatment response rates were high (>70%) and there were no significant difference in treatment response or durability of disease comparing sirolimus to vincristine. Our results support individualized treatment decision plans depending on clinical scenario and patient/physician preferences. Response criteria and response rates reported here will be useful for guiding future treatment protocols for vascular tumors.

Background: Maintaining dose-dense, interval-compressed chemotherapy improves survival in Ewing sarcoma patients but is limited by myelosuppression. Romiplostim is a thrombopoietin receptor agonist that may be useful in the treatment of chemotherapy-induced thrombocytopenia (CIT). Methods: Patients aged between 3 and 33 years with Ewing sarcoma from 2010-2020 were reviewed. CIT was defined as a failure to achieve 75,000 platelets per microliter by day 21 after the start of any chemotherapy cycle. Fisher exact test was used for univariate analysis and Pearson’s correlation coefficient was used for the association between continuous variables. Results: 27 out of 42 patients (64%) developed isolated CIT, delaying one to four chemotherapy cycles per patient. CIT occurred during consolidation therapy in 24/27(88.9%) and with ifosfamide/etoposide cycles in 24/27 (88.9%). Univariate analysis failed to identify risk factors for CIT. The use of radiation approached significant (p value=0.056). Ten patients received romiplostim. The median starting dose was 3 (range 1-5) mcg/kg. Doses were escalated weekly by 1-2 mcg/kg to 4-10 mcg/kg and continued throughout chemotherapy. A higher romiplostim dose was associated with a higher change in average platelet counts from baseline r= 0.73 (p=0.04). No romiplostim-related adverse events were identified aside from mild headache. Conclusions: CIT is the primary reason for the inability to maintain treatment intensity in Ewing sarcoma. The concurrent use of romiplostim with chemotherapy is safe and feasible, and efficacy was associated with higher romiplostim doses.

Purpose Pediatric patients with metastatic solid tumors historically have a poor overall survival. Some pediatric patients may still be potentially curable with aggressive local therapy to metastatic disease. The purpose of this study is to report results of the use of SBRT in the treatment of pediatric metastatic disease. Materials and Methods Pediatric patients who received SBRT between the years 2000-2020. Study endpoints included local control (LC), progression free survival (PFS), overall survival (OS), cumulative incidence (CI) of death or local failure and toxicity. The endpoints with respect to survival and LC were calculated using the Kaplan-Meier estimate. The cumulative incidence of local failure was calculated using death as a competing risk. Results 16 patients with 36 lesions irradiated met inclusion criteria. The median OS and PFS was 17 months and 15.7 months, respectively. The 1-year OS was 75%. The 6- and 12-month LC was 85% and 78%, respectively. There were no local failures in lesions receving a BED10≥100 Gy. Patients who had ≤5 metastatic lesions at first recurrence had a superior 1-year OS of 100% versus 50% with >5 lesions. One patient (6.3%) experienced a grade 3 CNS toxicity. Conclusions LC was excellent with SBRT delivered to metastatic disease, particularly for lesions receiving a BED10≥100 Gy. High-grade toxicity was rare in our patient population. Patients with ≤5 metastatic sites have a significantly better OS compared to >5 sites. Future prospective trials with multi-institutional collaboration will be necessary to evaluate appropriate patient selection and the optimal radiation dose regimen.