Minimal residual disease (MRD) measured by flow cytometry is highly prognostic in pediatric B-precursor acute lymphoblastic leukemia (B-ALL).
While intensive therapy changed the timing of relapse, it did not overcome the poor prognostic significance of MRD, according to an article in Blood published online ahead of print.
Researchers from the Children’s Oncology Group study AALL0232 investigated MRD in patients randomized to receive either high-dose methotrexate (HD-MTX) or Capizzi methotrexate (C-MTX) during interim maintenance, or prednisone or dexamethasone during induction.
Those with end induction MRD ≥0.1% or those with morphologic slow early response were assigned to receive a second interim maintenance and delayed intensification phase.
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Patients with end induction MRD <.01% demonstrated a 5-year event-free survival of 87+ 1% compared with those who had MRD 0.01%–0.1% who demonstrated 74+ 4%. Increasing MRD amounts were associated with worse outcomes.
Patients whose MRD was negative by end consolidation had a relatively favorable 5-year disease-free survival compared with those who had MRD ≥0.01%.
HD-MTX was superior than C-MTX, however neither retained prognostic significance. Intensified therapy administered to those with MRD >0.1% showed no 5-year event-free survival or overall survival benefit, but subjects who received it showed an early relapse rate similar to that in MRD-negative patients. Other therapies targeting MRD may further improve outcomes, however further study is necessary.