Treatment for a high-risk group for childhood acute lymphoblastic leukemia

Chemotherapy regimens for high-risk (HR) groups for childhood acute lymphoblastic leukemia (ALL) are briefly reviewed in this study. For patients with B-precursor ALL, the HR category includes patients more than 10 years of age who have a WBC count at diagnosis of more than the 50,000/microliter that is becoming a global standard for HR classification. Since 1981, the Children's Cancer and Leukemia Study Group (CCLSG) has developed a series of protocols for HR-ALL. These include the H811, H851, H874, H/HH911 and more recent H/HH941 protocols. With the H874 protocol in particular, patient outcomes with new intensive regimens strengthened by early treatment with cyclophosphamide (CPM) plus cytosine arabinoside (Ara-C), and reinduction therapy with THP-adriamycin, vincristine, prednisone and L-asparaginase seem to be better than outcomes of patients with the previous protocols. An intermediate-dose of CPM plus Ara-C showed a significantly higher event-free survival (EFS) rate than a high-dose regimen with the same drugs. The EFS rates at 4 years based on the H941 and HH941 protocols were 72.8% and 62.8%, respectively. Although the various prognostic factors for acute myelogenous leukemia (AML) have been inconsistent, bone marrow chromosome abnormalities including monosomy 7 an 11q23 rearrangement have become indicators for a poor prognosis, whereas patients with t (15; 17), t (8; 21) and inv (16) have a decreased likelihood of relapse after achieving remission. The 11q23 abnormality is a very important prognostic factor for infant acute leukemia. Based on these findings renewal protocols for AML, including hematopoietic stem cell transplantation, have been conducted by our CCLSG and other study groups.