MRD response to AEP
To evaluate the efficacy of AEP treatment in the context of induction failure we monitored MRD in 21 patients presenting a failure of remission EOI prior and after AEP. In eight patients (31 %) a profound MRD reduction of at least half a log-fold was observed. It should be emphasized here that 5 of these 8 patients had a T-ALL immunophenotype. The remaining 13 patients (including 7 patients with a T-ALL) did not discernibly respond to AEP treatment at the molecular level, with no patient showing a serious increase in disease burden (table 2).
In patients within the HR-I arm MRD assessment was performed after the consolidation phase at the start of delayed intensification. In 44 of the 77 HR-I patients that had received AEP MRD results were available. Of these 44 patients 38 (86%) had no measurable MRD, 2 patients had discernible but non-quantifiable (n.q.) MRD levels and only 4 patients still had quantifiable MRD burden. Fifteen of the 77 patients (19%) in the HR-I cohort who had received AEP suffered from relapsing disease. Interestingly, only 2 of those relapse-fated 15 patients showed a positive MRD at the start of delayed intensification, i.e. after AEP, whereas 7 of them showed negative results indicative of a declining predictive power of MRD negativity over time of treatment. In 6 patients who later on relapsed the MRD measurement was not available.