TKI Therapy Based on Molecular Monitoring in Allogeneic-HSCT Recipients With Philadelphia Chromosome-positive Acute Lymphoblastic Leukemia

The purpose of this study is to evaluate the efficacy of tyrosine kinase inhibitor(TKI) therapy based on molecular monitoring of BCR/ABL levels in Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL)undergoing allogeneic hematopoietic stem cell transplantation(allo-HSCT).

Philadelphia chromosome (Ph) is a reciprocal chromosomal translocation t(9;22）(q34;q11), which leads to the formation of the BCR/ABL oncogene. Ph is the most frequent cytogenetic abnormality in ALL characterized by poor outcome. With the BCR/ABL protein TKI, imatinib, in the combination chemotherapy regimes for newly diagnosed Ph+ ALL, more than 95% of patients can achieve complete remission(CR). Several studies have shown decreased relapse rates and improved disease-free survival for patients with imatinib-based treatment prior to allo-HSCT. However, the efficacy of maintenance therapy with imatinib after transplant for Ph+ ALL patients is still uncertain. In addition, acquired resistance to imatinib is frequently caused by point mutations in BCR/ABL that inactivate imatinib. Detection of minimal residual disease (MRD) after transplant is associated with an increased risk of relapse. Reverse transcription-polymerase chain reaction (RT-PCR) is a sensitive method for detecting low-level BCR/ABL transcripts to assess MRD in Ph+ ALL. It has been corroborated by several reports that detection of MRD after SCT was predictive of imminent relapse. In this study, we will evaluate the safety and efficacy of TKI therapy, when initiating treatment based on BCR-ABL transcript levels after allo-HSCT.