1. Department of Hematology Nippon Medical School 1‐1‐5 Sendagi, Bunkyo‐Ku Tokyo 113‐8603 Japan
2. NPO Millefeuille Childhood Cancer Frontiers 2‐15‐2‐124 masago Chiba‐City Chiba 261‐0011 Japan
3. Department of Hematology/Oncology Chiba Children's Hospital 579‐1 heta‐cho Chiba‐City Chiba 266‐0007 Japan
4. Department of Pediatrics Nippon Medical School 1‐1‐5 Sendagi, Bunkyo‐Ku Tokyo 113‐8603 Japan