MRD response and event-free survival according to combined MRP4 genotypes. Ansari et al¹  distinguish 3 groups: group 1, with TC-1393 and CC or AC934 genotypes; group 2, with TT-1393 and CC934, and group 3, with TT-1393 and AC934 genotypes. (A) Frequency of MRD positivity at treatment week 16 (after first application of 6-Mercaptopurine and high-dose MTX). MRD positivity and MRD positivity below quantitative range were defined according to ESG criteria. For details, see van der Velden et al.⁶  (B) The number of patients in each curve as well as the P value, estimated by log-rank test for the survival differences between the patients groups, is indicated on each plot. Disease-free survival (DFS) was calculated as the interval between first documented complete remission and relapse or end of observation. Patients who underwent stem cell transplantation in first remission, patients with premature termination of first-year treatment and patients who died in complete remission were included but censored at the date of event. Patients who died during remission induction or who did not complete induction treatment were excluded from the analysis. The probability of DFS was estimated by the method of Kaplan and Meier.