Treatment regimens and treatment response
One hundred and seventy out of 173 patients, including 75 children and 95 adults, received one to two cycles of induction therapies: 103 on anthracyclines combined with cytarabine (AA), 54 on either FLAG+IDA or DAE, and 13 on other regimens. Detail was documented in table 1. AA was the main induction regimen in adults, while intensive regimen FLAG+IDA or DAE was mainly used in children (adults vs. children: AA, 89/95, 93.7% vs. 14/75, 18.7%; FLAG+IDA/DAE, 0 vs. 54/75,72.0%, P<0.001). After two cycles of induction therapies, cumulatively 155/170 (91.1%) patients achieved CR. CR was much higher in children (children 73/75, 97.3% vs. adults 82/95, 86.3%, P=0.012). For those who received AA regimen, there was no statistical difference in CR rate between the two age groups (children 13/14, 92.9% vs. adults 78/89, 87.6%, P=0.572).
Univariate analysis revealed that age (hazard ratio [HR] 5.787, 95% confidence interval [CI] 1.263-26.504, P=0.024) and FLT3-ITD mutation (HR 6.100, 95% CI 1.323-28.129, P=0.020), but not gender, EML, peripheral WBC count, immunphenotype, additional chromosomal abnormalities (ACAs) or c-KIT mutations, were the adverse factors for CR. Multivariate analysis showed that the FLT3-ITD mutation (HR 23.240, 95% CI 1.202-449.293, P=0.037) was the only independent poor prognostic factor. However, when induction therapies were taken into account, none of the above were identified as unfavorable per multivariate analysis (P>0.05).
Cumulatively, a total of 160 out of 170(94.1%) patients achieved CR. The CR in children occurred in 74/75(98.7%) patients and that in adults was much lower in 86/95(90.5%) patients (P=0.025). All CR patients then received a median of 4 (1-11) cycles of consolidation therapies. Pediatric patients were mainly treated with MDAC-based regimen (55/74, 74.3%), while SDAC-based (47/86, 54.7%) and MDAC-based regimens (39/86, 45.3%) were given to adult patients (P<0.001). Patients who required salvage therapy or allo-transplant were comparable between the two age groups (Table 1).
With a median follow-up of 20 (2-96) months, 112 out of 170 patients survived and 58 died: 40 from disease relapse, 10 from lack of response, and 8 due to treatment-related mortality. Of the 160 patients who achieved CR, 55 relapsed. For the entire study cohort, the cumulative incidence of relapse (CIR) was 28.3%±3.9%, the DFS 65.4%±3.9% and OS 69.9%±3.8%. The 2-year CIR, DFS and OS were 32.8%±4.1%, 60.5%±4.1% and 65.5%±4.1%, respectively.