Abstract
The 8511 protocol was designed to answer the following questions for children with standard-risk acute lymphoblastic leukemia (SR-ALL). (a) What is the frequency of central nervous system (CNS) leukemia in SR-ALL without presymptomatic cranial irradiation therapy ? (b) Could intensive rotational combination chemotherapy improve overall outcome of SR-ALL ? (c) Could the active immunotherapy have any beneficial effect on the clinical outcome ? Eighty-five evaluable patients were registered and complete remission was successfully achieved in 83 out of 85 cases. All responders were randomized to standard maintenance regimens with or without immunotherapy (protocol A or B respectively), or intensive rotational combination regimen (protocol C). No difference was found in both the rate of event-free survival (EFS) and the site of relapse between protocol A and B, indicating that immunotherapy has no beneficial effect on the overall outcome, although long-term follow-up is apparently necessary. The overall rate of solitary CNS relapse was 9.6% (8 of 83 cases). The frequency of CNS relapse was similar in each maintenance protocol. Interestingly, EFS rate of the patients with lower leukocyte count (<10, 000/μl) was significantly higher than that with higher leukocyte count (≥10, 000/μl) in protocol A and B, but not in protocol C. In the group with lower leukocyte count, estimated EFS rate in protocol A and B (74.8% and 79.2% respectively) was higher than that in protocol C (50.6 %). In contrast, in the group with higher leukocyte count, EFS rate within 5 years in protocol C was significantly higher than those in protocol A and B (p < 0.05). These data suggest that SR-ALL could be further divided into subgroups according to the leukocyte count. Intensive rotational combination chemotherapy might be more effective for the group with relatively higher leukocyte count.
