Results of acute lymphoblastic leukemia therapy in childhood: GDR-experiences 1981-1987

The multidrug resistance-associated protein 3 (MRP3) is associated with a poor outcome in childhood ALL and may account for the worse prognosis in male patients and T-cell immunophenotype

The family of multidrug resistance-associated proteins (MRPs) belongs to the superfamily of adenosine triphosphate-binding-cassette (ABC) transporters, which have the ability to function as outward pumps for chemotherapeutic drugs and therefore might be involved in drug resistance. In this study the expression of the MRP2, MRP3, MRP4, MRP5, and SMRP genes was measured using TaqMan real-time polymerase chain reaction (PCR) in 103 children with previously untreated acute lymphoblastic leukemia (ALL) (precursor B-cell ALL [B-ALL], n = 71; T-cell ALL [T-ALL], n = 32). All 5 genes were expressed with a great variability. Only MRP3 expression was associated with a significantly worse prognosis (P =.008). The median expression of MRP3 was 10-fold higher in T-ALL than in precursor B-ALL (P <.001) and 4-fold higher in male patients than in female patients (P <.001). The prognostic impact of MRP3 was independent of immunophenotype or sex. Higher levels of MRP3 were found in patients with a poor in vivo response to prednisone, but this could not be confirmed in an independent case-control study (40 patients) for prednisone response. In healthy donors, the median expression of MRP4 was 4-fold higher in bone marrow and 8-fold higher in CD34+ stem cells compared with peripheral blood (P =.002). Our results suggest that MRP3 is involved in drug resistance in childhood ALL. It therefore represents an interesting target to overcome multidrug resistance. High levels of MRP3 could possibly be the reason for the poorer prognosis of male patients or patients who have T-ALL. Similar to other members of the family of ABC transporters, MRP4 seems to be a marker for immature stem cells.

CNS-directed therapy for childhood acute lymphoblastic leukemia: Childhood ALL Collaborative Group overview of 43 randomized trials

PURPOSE

A collaborative meta-analysis was performed to clarify the relative effects on relapse and survival of different types of therapies directed at the CNS in childhood acute lymphoblastic leukemia.

MATERIALS AND METHODS

Data were sought for each individual patient in all trials started in or before 1993 that included unconfounded randomized comparisons of such treatments. Log-rank survival analyses were performed for each trial, and overall results for groups of trials addressing similar questions were obtained from the totals of the observed minus expected number of events and their variances.

RESULTS

Radiotherapy and long-term intrathecal therapy gave similar outcomes, with no significant difference in event-free survival despite random assignment of treatment to 2,848 patients, 1,001 of whom suffered relapse or death. Intravenous methotrexate reduced non-CNS rather than CNS relapses, and hence, the addition of intravenous methotrexate to a treatment regimen including radiotherapy or long-term intrathecal therapy improved event-free survival, with a 17% reduction in the event rate (95% confidence interval, 6% to 27%; P =.003). The event-free survival at 10 years in these trials was 61.9% without intravenous methotrexate and 68.1% with intravenous methotrexate. There was no significant difference in survival (14% death rate reduction; P =.09). There were insufficient randomly assigned patients to adequately address other questions, such as effect of different doses. No evidence was found of differences, between trials or between subgroups of different types of patients, in the relative effects of treatment.

CONCLUSION

Radiotherapy can be replaced by long-term intrathecal therapy. Intravenous methotrexate gives some additional benefit by reducing non-CNS relapses.