BCR-ABL1 transcripts (MR^4.5) at post-transplant 3 months as an early predictor for long-term outcomes in chronic myeloid leukemia

Background/Aims: The aim of this study was to identify the role of BCR-ABL1 transcript level as a predictor for post-transplant relapse and outcome in patients who underwent allogeneic stem cell transplantation (SCT) for chronic phase (CP) chronic myeloid leukemia (CML). Methods: Of 101 patients receiving allograft in CML CP, 85 had available quantitative reverse transcriptase polymerase chain reaction data at post-transplant 3 months. These patients were divided into two groups according to molecular response (MR^4.5), defined as a BCR-ABL1 transcript level ≤ 0.0032% on the international scale, at 3 months based on receiver operating characteristic curve analysis of relapse. Results: The 4-year overall survival and event-free survival (EFS) were 80.6% and 57.3%, respectively, and the cumulative incidence of relapse at 4 years was 29.6% after a median follow-up of 126.4 months. We performed multivariate analyses including potential variables to evaluate the early predictive role of MR^4.5 at 3 months and found that MR^4.5 at 3 months was associated with a higher EFS (p = 0.028) and showed a trend for a lower relapse rate (p = 0.089). Conclusions: our results imply that frequent molecular monitoring and immune suppressive therapy modulation are required for patients without reduction of BCR-ABL1 transcripts to this level after SCT.