According to a retrospective analysis of data from 175 patients with acute myeloid leukemia (AML) treated at Moffitt Cancer Center in Tampa, Florida, bone marrow hypocellularity of <20% at day 14 following primary induction is the most important factor associated with achievement of complete remission (CR) and longer overall survival (OS) in patients who receive second induction due to residual disease. This analysis was intended to identify variables that might predict improved outcomes following second induction.
The rate of CR following second induction was 72.4% for patients with marrow hypocellularity <20% at day 14, compared with 42.6% in patients without hypocellularity (P≤.001). The CR for the entire study population was 59%. Absolute blast reduction of >50% and de novo disease status were also significantly correlated with achievement of CR following reinduction, but there was no association with age, cytogenetic risk, use of a high-dose cytarabine–containing regimen, and length of retreatment delay. An absolute reduction in blast count of >50% was associated with CR in a univariate analysis, but this association did not retain statistical significance in a multivariate analysis.
The median OS for the entire study population was 12.4 months, but achievement of CR was associated with a significant improvement in OS (19.1 months vs 7.2 months; P<.001). Bone marrow hypocellularity <20% at day 14 was associated with a significant improvement in OS compared to patients without hypocellularity (14.8 months vs 8.4 months; P = .001). Other variables associated with significant improvements in OS included age, de novo disease status, and cytogenetic risk. Univariate analysis identified a correlation of nadir marrow cellularity and absolute nadir marrow blast reduction with OS, but this correlation was not supported by multivariate analysis.
In their conclusion, the authors commented on the importance of this study, noting that determination of factors that predict failure to achieve CR following second induction could potentially spare patients from unnecessary chemotherapy, and identify patients for whom novel treatment approaches might be more important. Although the study is limited by its retrospective nature, the authors indicated that a randomized controlled trial would be unlikely and that this study was unique in its attempts to identify factors to guide treatment decisions in AML.