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Aim. To evaluate the efficiency of the original ALL-MB-2002 protocol within the multicenter study of treatment of acute lymphoblastic leukemia (ALL) in children. Subjects and methods. A total of 1873 primary patients with ALL aged 1 to 18 years, of whom 1544 patients were enrolled in this study, were notified at 36 clinics of Russia and Belarus from April 15, 2002, to January 1, 2008. Results. With the median observation of 4.12 years, 7-year event-free survival (EFS) was 73±13%; overall survival (OS) 78±2%; relapse-free survival 82±1%. The rates of EFS and OS were equal and amounted to 76±2 and 80±2% in the standard-risk group (SRG) and intermediate-risk group (ImRG), respectively. In the high-risk group (HRG) patients, EFS and OS were as high as 30±6 and 37±6%, respectively. The frequency of relapses with central nervous system lesion was as much as 4.7% in all the patients, 6-year cumulative risk for isolated neurorecurrences being 2.5% in the SRG patients. Adolescents, patients with the baseline leukocytosis (more than 100109/l), and those with a splenic size of over 4 cm or more from the costal arch margin had substantially worse survival rates. A poor early response to therapy (on induction days 8 and 15) was also associated with its lower efficiency. Conclusion. Despite a considerable rise in the number of centers and a slight increase in the intensity of therapy, the results of the new ALL-MB-2002 protocol are as minimum equivalents obtained in the use of the previous ALL-MB-91 protocol. A significant improvement in the overall results of therapy and a reduction in the cumulative risk for isolated neurorecurrences were noted in the ImRG patients.

The paper presents the results of a multicenter randomized study of two-dose COLI-ASP regimens in therapy of consolidation of standard risk-group (SRG) children and adolescents with acute lymphoblastic leukemia (ALL) treated by the ALL-MB-2002 protocol. The principal aim of the study was to elucidate whether the dose of COLI-ASP might be reduced without losing the efficiency of therapy. The analysis covered primary ALL patients notified at 36 clinics of Russia and Belarus, enrolled for the study in the period of May 1, 2002, to October 10, 2006. Out of 819 patients to be examined, 414 received COLI-ASP in a dose of 10,000 U/m2 (a control group), and 405 children took it in a dose of 5,000 U/m2 (a study group). No statistically significant differences were found between the patients in gender, age, baseline leukocytosis, and spleen size. The study showed no statistically and clinically significant differences in event-free, overall, and relapse-free survival (EFS, OS, and RFS, respectively) and relapse rates with the use of two-dose COLI-ASP regimens. However, in the control group, the death rate in remission was twice greater than that in the study group (p = 0.02). Detailed analysis of the outcomes of therapy in some subgroups revealed no differences between the control and study groups. The Cox multiple regression analysis has indicated that the factors influencing EFS and RFS are the baseline sizes of the spleen, baseline leukocytosis, age, and a response to treatment in the period of induction, rather than the dose of E. coli asparaginase. The authors have also found that among the SRG patients, there is a subgroup of patients without risk factors, in whom the reduction in the COLI-ASP dose may substantially increase survival rates, by lowering toxicity and mortality in remission.

The use of all-trans retinoic acid (ATRA) drastically improved the results of therapy for acute promyelocytic leukeimia (APL). The high efficiency of the Russian protocol APL-93—98 applied to 62 children and adolescents with APL (event-free and overall survival (EFS and OS) were 84±5% respectively with a relapse rate of 7%) was achieved, by administering the high cumulative dose of daunoruicin (495 mg/m2) and single doses of АТRА (45 mg/m2). In this connection, the APL-2003 protocol attempted to reduce both acute and chronic toxicity of the therapy, by decreasing the cumulative dose of daunorubicin to 405 mg/m2 and the single dose of АТRА to 25 mg/m2 under regular control of minimal residual disease via molecular monitoring of the specific transcript PML/RARα. Analysis of the results of treatment in 61 patients aged 1.3 to 17 years (median 11.3) showed that despite of the reduced protocol intensity, the efficiency of therapy did not generally reduce — EFS and OS were 79±6 and 93±3%, respectively. The likelihood of the development of a relapse was significantly affected by molecular resistance, i.e. the retention of the transcript PML/RARα before a phase of maintenance therapy: the recurrence risk in this group was 57% whereas there were no differences in all cure rates between the patients depending on baseline leukocytosis. All 6 patients with relapses were treated with arsenic trioxide, resulting in not only clinical and hematological, but also molecular remissions; thereafter the patients received myeloablative therapy and autologous hemopoietic stem cell transplantation. The second remission lasted 3 to 24 months. Thus, reducing the cumulative dose of anthracyclines and the dose of АТRА did not make the results of the therapy for APL worse. The monitoring of minimal residual disease before and during maintenance therapy is a mandatory component of successful treatment in APL patients. Arsenic trioxide is an effective agent for the treatment of APL relapses.

191 consecutive unselected children with acute lymphoblastic leukemia aged from 1 to 16 years were enrolled in the study. Bone marrow samples were obtained at the time of initial diagnostics as well as at days 15 (n = 188), 36 (n = 191), and 85 (n = 187) of remission induction. Minimal residual disease (MRD) was assessed by 6–10-color flow cytometry. Flow cytometry data at day 15 allowed distinguishing three patients groups with significantly different outcome (p ˂ 0.0001): 35.64 % patients with MRD < 0.1 % represented 5-year event-free survival (EFS) of 100 %; 48.40 % cases with 0.1 % ≤ MRD< 10 % had EFS 84.6 ± 4.2 %; 15.96 % patients with very high MRD (≥ 10 %) belonged to group with poor outcome (EFS 56.7 ± 9.0 %). At the end of remission induction (day 36) 36 children (18.85 %) with MRD higher than 0.1 % had significantly worse outcome compared to remaining ones (EFS 49.4 ± 9.0 and 93.5 ± 2.1 % respectively; p ˂ 0.0001). From a clinical standpoint it is relevant to evaluate both low-risk and high-risk criteria. Multivariate analysis showed that day 15 MRD data is better for low-risk patients definition while end-induction MRD is the strongest unfavorable prognostic factor.