Retrospective Analysis of 59 Cases FLT3-ITD Mutation Positive Acute Myeloid Leukemia

Objective: Between October 2010 to May 2014, 59 patients who diagnosed as FLT3-ITD positive aAML were analyzed. All the patients were signed informed consents to agree to provide their clinical information to this study. Informed consents were approved by Ethics Committee. Peripheral white cell count at diagnose; complete remission (CR) rate; the percentage of progressing to refractory leukemia and the response to allogenic stem cell transplantation (allo-SCT) were analyzed. Better therapeutic strategy was explored.

Methods: Diagnosis was made according to the French-American-British classification system or World Health Organization diagnostic classification criteria. FLT3-ITD mutation was detected by polymerase chain reaction (PCR) and gel electrophoresis. Refractory leukemia is defined as fail to achieve CR after two courses of conventional chemotherapy, or with a short (<6–12 months) CR1 duration, or patients who have relapsed at least twice.

Results: 59 patients were diagnosed as Flt3-ITD mutation positive aAML in our centre during the last 44months, including 30 males and 29 females, with an average age at 42.2y. Flt-ITD mutation can be detected in 1/59 of M0 (1.7%); 6/59 of M1 (10.1%); 20/59 of M2 (33.8%); 9/59 of M3 (15.2%); 5/59 of M4 (8.5%); 14/59 of M5 (23.7) and 1/59 of M6 (1.7%). 23.7% (14/59) patients had high white blood cell counts (＞100*10E9/L) at diagnose. After induction chemotherapy, 50% (27/54) cases achieved CR. 53.4% (23/43, 16 cases were lost follow-up) patients met the criteria of refractory leukemia. 12 patients received allo-SCT, including 8 refractory leukemia cases. The average time from diagnose to transplantation is 6.5 months (3 to 12 months). 1 patient relapsed at 3 months after allo-SCT who was diagnosed refractory leukemia before allo-SCT, all other 11 cases remained CR with the longest follow-up time at 26 months (3 to 26 months). For the left 15 refractory leukemia cases who did not received allo-SCT, the 1-year OS rate for the 12 cases is 50% (6/12), but the 1-year EFS rate is 0 (0/12) (3 cases were lost follow-up).

Conclusion: FLT3-ITD mutation was reported to be detected in around 30% of aAML. Flt3-ITD mutation is an independent high-risk factor for aAML. Based on retrospective data from 59 cases in our centre, FLT3-ITD mutation positive aAML patients can be characterized as high white blood cell count at diagnose, lower CR rate and higher refractory leukemia percent. allo-SCT can achieve persistent remission in part of patients, even in refractory leukemia patients. Our study also implied that the CR1 is the ideal stage for FLT3-ITD mutation positive aAML patient to receive allo-SCT.