Determinants of outcome after intensified therapy of childhood lymphoblastic leukaemia: results from Medical Research Council United Kingdom acute lymphoblastic leukaemia XI protocol

The single most important prognostic determinant in childhood acute lymphob lastic leukaemia (ALL) is effective therapy and changes in therapy may infl uence the significance of other risk factors, The effect of intensified the rapy on the importance of currently recognized phenotypic and genotypic det erminants of outcome was assessed in 2090 children enrolled on the Medical Research Council United Kingdom acute lymphoblastic leukaemia XI (MRC UKALL XI) protocol. Treatment allocation was not determined by risk factors. Mul tivariate analysis confirmed the dominant influence on prognosis of age, se x and presenting white cell count (WCC), After allowing for these features, blast karyotype, d 8 marrow blast percentage and remission status at the e nd of induction therapy were the only remaining significant predictors of o utcome. Organomegaly, haemoglobin concentration, French-American-British ty pe, body mass index, presence of central nervous system disease at diagnosi s, immunophenotype and presence of TEL/AML1 fusion gene (examined in a subs et of 659 patients) either had no significant effect on outcome or were sig nificant only in univariate analysis, Among karyotype abnormalities with an independent influence on prognosis, high hyperdiploidy (> 50 chromosomes) was shown to be favourable, whereas near haploidy (23-29 chromosomes), pres ence of the Philadelphia chromosome, t(4;11) and abnormalities affecting th e short arm of chromosome 9 [abn (9p)] were adverse risk factors. Early res ponders to therapy, determined by residual marrow infiltration after 8d of induction therapy, had a good outcome, while the small proportion of patien ts who did not achieve a complete remission by the end of induction therapy had a poor outcome. A third block of late intensification was shown to imp rove event-free survival by 8% at 5 years. The effect of these risk factors was not significantly different between those randomized to the third inte nsification block and those not randomized to a third block.