EPT-09: TANDEM THIOTEPA-BASED CONDITIONING AND AUTOLOGOUS STEM CELL TRANSPLANTATION IN CHILDREN WITH HIGH-RISK CENTRAL NERVOUS SYSTEM TUMORS

High-risk (HR) central nervous system (CNS) tumors characterized by poor long-term survival. High-dose chemotherapy (HDCT) including high-dose thiotepa (TT) may improve the prognosis in HR pts. From 2012 till 2016 18 pts (HR medulloblastoma - 11 with, ATRT - 3, anaplastic ependymoma - 3 and 2 with PNET) received tandem HDCT including TT 600 mg/m2/cycle (for pts under 36 months - 10 mg/kg) and carboplatin (Carbo) 1020 mg/m2/cycle (for pts under 36 months - 17 mg/kg) followed by AutoSCT. The median age was 6 (2 - 20) years. As program induction all pts had got 2-3 courses of CT and age-adjusted RT. The median interval between cycles was 42.6 (29 - 55) days. The median number of grafted CD 34+ cells was 3.25 (1.5 - 6.3)*106/kg after each cycle. All pts experienced fast and prompt hematological recovery with a median number of 10 days (8 - 15) and 15 days (10 -30) to reach WBC > 1x109/l and Plt > 20x1011/l after 1st HDCT, and 11 days (8 - 25) and 18 days (12 - 30) after 2nd HDCT, respectively. Toxicity was mild with no difference between 1st and 2nd HDCT cycles. No toxic death was observed. Six pts relapsed in 16 (5 - 32) mos. after end of treatment. Twelve pts are alive with no signs of progression (8 pts in CR). Overall survival is 72.2%. Event-free survival is 66.6%. Tandem HDCT including 1200 mg/m2 of TT seems to be safe and effective tool in patients with HR CNS tumors.