Survival and statistical analysis
The overall survival (OS) was calculated from the day of diagnosis to the day of death or the last follow-up, and the disease free survival (DFS) from the day of diagnosis to the day of relapse or the last follow-up. CR was defined as bone marrow blasts less than 5% irrespective of peripheral blood cell recovery.
Statistical analyses were performed using SPSS 20.0. Not normally distributed data were described by the median. A comparison of distribution between two groups of data was performed by a Mann-Whitney nonparametric U test, and correlations between two variables were performed by Spearman rank correlation analysis. The Kaplan-Meier method was used to estimate median survival and survival probabilities, and associations with covariates were tested by the log-rank test. Multivariate analysis was performed to identify independent prognostic factors adopting Cox regression model. P<0.05 was considered to indicate a statistically significant difference.