Acute lymphoblastic leukemia in children: treatment planning via minimal residual disease assessment.

BACKGROUND Acute lymphoblastic leukemia (ALL) is the most common type of cancer in children and adolescents, accounting for 30% of all cases of malignancy in this age group. The cure rate of ALL is now above 80%. The clinical and biological characteristics of ALL that have been studied to date are of limited use in predicting the individual response. Newly developed methods for the assessment of minimal residual disease (MRD) are more helpful in this regard. METHODS Review of pertinent literature retrieved by a selective search in Medline. RESULTS MRD assessment has gradually been incorporated into ALL treatment planning over the past two decades. In the largest study to date of the use of MRD for this purpose, which included 3648 children with ALL, the MRD status on days 33 and 78 after the start of treatment was found to be the most important prognostic factor. The study group included 3184 patients with B-precursor ALL (leukemia consisting of immature B-lymphocytes), of whom a large subgroup (standard risk profile, 42%) had a seven-year event-free survival rate (7Y-EFS) of 91.1%; for the 6% of B-ALL patients with a high-risk profile, the cumulative rate of recurrence was 38.5 %.The remaining 464 patients had T-ALL (leukemia consisting of T-lymphocytes). The leukemia cells were eliminated more slowly overall in these patients than in those with B-ALL. Nonetheless, the T-ALL patients with a standard risk profile (16% of all T-ALL patients) had an excellent 7Y-EFS rate (91.1%), while the high-risk group (21% of all T-ALL patients) had an MRD recurrence rate of 37.7%. These findings are representative of current data from around the world on children and adults with ALL. CONCLUSION MRD analysis enables more accurate prediction of ALL patients' response to treatment. Risk-group stratification by MRD assessment has already brought about considerable improvement in individualized treatment planning.