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Results of three consecutive completed UK trials (1980–1997) for childhood lymphoblastic leukaemia are presented. National accrual has progressively increased so that over 90% of all the country's ALL cases were treated on the latest trial reported, UKALLXI. From 1980 to 1990, event-free and overall survival progressively improved, following adoption of an American therapy template and use of two post-remission intensification modules. Since 1990 despite demonstration of the benefit of a third intensification module overall event-free survival (EFS) has not improved further. Survival remains high due to a good retrieval rate especially for those relapsing off treatment after receipt of two intensification pulses. Possible reasons for the plateau in event-free survival (including type and dose of induction steroid, dropping of induction anthracycline, type and dose of asparaginase, gaps early in therapy following intensification, and overall lack of compliance in maintenance) are being explored in the latest protocol ALL ’97. Cranial irradiation had been successfully replaced by a long course of intrathecal methotrexate injections for the majority of patients. Age ( 10 years) sex (male) and white count >50 × 109/l plus slow initial bone marrow clearance were consistently the most important independent prognostic indicators during this time period. Rome/NCI criteria accurately predict standard and high-risk groups for B cell lineage, but not consistently for T cell disease. This international collaborative venture might help us to define those truly at highest risk, and how we can optimise therapy for specific subgroups including T-ALL and those with unfavourable cytogenetics.

The effects on long-term outcome in childhood acute lymphoblastic leukaemia (ALL) of the duration and the intensity of maintenance chemotherapy need to be assessed reliably. With this objective the Childhood ALL Collaborative Group coordinated a worldwide overview of all randomised trials that began before 1987.Individual patient data were sought for about 3900 children in trials of longer vs shorter maintenance (eg, 3 vs 2 years), 3700 in trials of intensive "reinduction" chemotherapy during maintenance, and 4400 in trials of various other questions, including 1300 in trials of pulses of vincristine and prednisone (VP) during maintenance. Analyses were of survival in first remission, overall survival, and cause-specific mortality.Deaths during remission were increased by longer maintenance (2.7 percent vs 1.2 percent), VP pulses (4.0 vs 3.2 percent), and intensive reinduction (4.8 percent vs 3.3 percent), but these increases were counterbalanced by reductions in relapses. Total events (relapse or death) were significantly reduced by longer maintenance (23.3 percent vs 27.6 percent), VP pulses (31.2 percent vs 40.4 percent) and intensive reinduction (27.8 percent vs 35.8 percent) (each 2p0.001). Many of those who relapsed were successfully re-treated, however, and only for intensive reinduction was overall survival significantly improved (18.5 percent vs 22.3 percent; 2p=0.01).Intensive reinduction chemotherapy in these trials produced an absolute improvement of about 4 percent in long-term survival; if the extra deaths in remission had been avoided, this would have been a 5 percent benefit. Further improvements in survival seem more likely to be obtained with intensive treatment than with longer low-level maintenance.