CLEARANCE OF MARROW INFILTRATION AFTER 1 WEEK OF THERAPY FOR CHILDHOOD LYMPHOBLASTIC-LEUKEMIA - CLINICAL IMPORTANCE AND THE EFFECT OF DAUNORUBICIN

At the commencement of UKALL XI, a national MRC trial for childhood ly mphoblastic leukaemia (ALL), the therapy included a bolus of daunorubi cin (DR) on the first 2 d of the protocol. This component of treatment was subsequently withdrawn because of concern about longterm cardioto xicity. All children both before and after this change of policy had t heir marrow status at the end of the first week assessed by central re view as part of the trial to examine the clinical importance of the ra te of disease clearance. This also afforded an opportunity to observe the effect of DR on gross residual disease at an early stage of therap y. 1419 children were studied: 342 received DR ('recipients'), 1077 di d not. 44% of the recipients completely cleared their marrow of blast cells after 8 d compared with 13% of the non-recipients (chi(2) = 158. 2, P < 0.0001). The difference in the proportion with massive residual disease (>80% blasts) was less impressive but there was still a diffe rence in favour of DR recipients (DR 9%, no DR 15%; chi(2) = 7.7, P = 0.006). The rate of disease clearance correlated with disease-free sur vival for both recipients and non-recipients, but there was no signifi cant difference in outcome when comparing the two groups with each oth er, either in term of disease-free or relapse-free survival. DR accele rated the rate of blast cell disappearance from the marrow but the dif ference this made to disease free survival is small or non-existent. I t appears to be the relative speed of response to a given therapeutic regimen that is prognostically important rather than the absolute rate of response when comparing one treatment with another.