OBJECTIVETo clarify the clinical, cytogenetical and molecular characteristics and prognosis of Ph(+) ALL patients with ABL kinase domain mutations (ABL-KDMs), and to evaluate the therapeutic value of allogeneic hematopoietic stem cell transplantation (allo-HSCT) combined with tyrosine kinase inhibitor (TKI) in these patients.

METHODSRetrospective analysis of clinical features, molecular genetic characteristics, mutation distribution and prognosis of newly diagnosed Ph(+) ALL patients with ABL-KDMs from February 2010 to August 2014 were performed, and the efficacy of treatment regimen of allo-HSCT combined with different TKIs was compared.

RESULTSOf 88 Ph(+) ALL patients during maintenance treatment stage for ABL-KDMs monitoring, mutation was detected in 42 patients with median time of 8 months from diagnosis to mutation occurrence. The median age of mutation group was 40-year-old, older than that of non-mutation group (32.5-year-old) (P=0.023). The incidence of complex chromosome abnormality of mutation group was higher than that of non-mutation group (P=0.043), with alternations in chromosome 7, 5 and +Ph more frequently observed. There were 21 types of mutation at 18 locations detected, with T315I mutation ranking the top followed by E255K/V, Y253H/F and E459K. Mutation group featured no significant difference in complete remission (CR) rate in contrast to nonmutation group, but was remarkably lower in major molecular remission (MMR) rate than non-mutation group. The 2 year and 5 year overall survival rate of mutation group was 45.4% and 35.0% respectively, much shorter than that of non-mutation group (67.8% and 63.3%), (P=0.047). The median survival of patients with T315I and E255K/V was 19 and 10 months, significantly shorter than that of patients with other mutations. Among the 42 patients with mutations, 14 underwent allo-HSCT, and the median survival was 29 months, longer than that of patients received chemotherapy alone (17 months) (P=0.024). Fourteen allo-HSCT patients were given nilotinib or dasatinib at the time of mutation occurrence, and there was no significant difference in the overall survival in contrast to patients who continue to take imatinib.

CONCLUSIONSABL kinase domain mutations are closely related to the older age and high genomic instability in the newly diagnosed Ph(+) ALL patients. Mutation types showed diversity and complexity, which remarkably affected patients' prognosis and survival. T315I and E255K mutations account for more than half of all cases, characterized by a less favorable prognosis. Currently, allo-HSCT is the only method that has the potential of elongating life expectancy, but the utility of second-generation TKI during relapse does not necessarily have an edge on survival over imatinib.