Treatment of childhood acute lymphoblastic leukemia after the first relapse: curative strategies

Treatment of recurrent childhood acute lymphoblastic leukemia (ALL) has been controversial in the last decade. Conventional intensive chemotherapy (CHEMO) can cure up to 30% of children who have relapsed after ALL: similar results have been obtained with autologous bone marrow transplantation (ABMT), but allogeneic bone marrow transplantation (AlloBMT) seems to be the best therapeutic option. In this review the authors point out the contribution of current strategy in the setting of children with ALL who experience a first relapse and should be offered optimal treatment in order to obtain the best disease-free survival (DFS). The principal objective of this issue is to reach a possible consensus on the more controversial points regarding factors considered strong predictors of the outcome of the relapsed patients, second-line chemotherapy, optimal timing and type of transplantation. EVIDENCE AND INFORMATION SOURCE: Data published in the literature over the last decade concerning early and late relapse in childhood ALL suggest that improvements in cure rates may be achieved by intensification of the relapse treatment both with chemotherapy and with different types of transplantation. An accurate search for Medline data has been performed in order to understand the risk-benefit ratio of aggressive therapy adopted in this setting.

Modern first-line treatment protocols for childhood ALL have contributed to curing an ever larger number of patients but this strategy could be responsible for creating a more resistant leukemic clone at the time of systemic or extramedullary relapse. This hypothesis emerges from a number of single or multicenter experiences; thus clinical and biological features in relapsed patients are being studied carefully in order to understand which risk-directed second-line therapy should be best adopted. The BFM group classified ALL relapses as "very early", "early", or "late" according to the time from diagnosis to first relapse (i.e. < 18, > 18 and < 30 or more than 30 months) and has shown that about 2/3 of the small fraction of children with late extramedullary relapses or late non T-marrow relapses or early combined non T-relapses can be rescued by chemotherapy; in contrast ALL early relapses or T-immunophenotype ALL relapses can be rescue only by AlloBMT. Since 1990 the AIEOP group adopted BFM-like first-line treatment and experienced similar situations for relapsed patients so that, even in absence of a real common relapse protocol, they went in the same direction as the BFM group as far as hematopoietic stem cell transplantation (HSCT) procedures and decision were concerned. A recent AIEOP study on the destiny of 192 consecutive patients with ALL in 2nd complete remission and not having an HLA suitable sibling donor is presented in this issue. The value of different HSCT procedures is addressed and the protection against a new relapse seems to be real, although, of course, the risk-benefit ratio should always be evaluated.

Very few prospective studies on the treatment of childhood ALL relapse have been set up in the last decade because of many difficulties regarding common second-line therapies, some reluctance versus HSCT in consideration of the transplant-related mortality and the so-called late effects. Additional modifications of allogeneic family and unrelated donor HSCT strategies and the promising results both of cord HSCT and auto-grafting methods including in vitro purging or post-transplant immunotherapy, are making transplantation procedures for ALL relapsed patients more appropriate and increasing confidence in their use. The possibility of performing common prospective international studies should be encouraged over the next years in order to elucidate an area of great research as is that of the treatment of childhood ALL relapse.