The significance of minimal residual disease kinetics in adults with newly diagnosed PML-RARalpha-positive acute promyelocytic leukemia: results of a prospective trial.

Seventy adults with acute promyelocytic leukemia were studied to clarify the significance of the level and kinetics of minimal residual disease (MRD) over their entire treatment course by realtime quantitative polymerase chain reaction. At a median follow-up of 44 months, nine relapses had occurred. The 5-year probabilities of relapse and disease-free survival were 17.3+/-5.4% and 81.5+/-5.4%, respectively. A MRD level of >10-3 after first consolidation was the most powerful predictor of relapse (85.7+/-13.2% versus 7.3+/-4.1%, p<0.001) and disease-free survival (14.3+/-13.2% versus 91.2%+/-4.3%, p<0.001). Prospective MRD monitoring may allow us to identify subgroups of patients at high risk of relapse earlier during treatment.