Prevalence and Prognostic Impact of CEBPA mutations in Children with AML Treated with the AIEOP-LAM 2002/01 Protocol.

Abstract 2643

Poster Board II-619

C/EBP is a transcription factor that regulates terminal granulocytic differentiation. CEBPA mutations have been associated with improved outcome in both adult and pediatric patients with acute myeloid leukemia (AML). However, the impact in different treatment protocols, as well as the different outcome between single and double mutants, is still to be definitively established. We evaluated the prevalence and prognostic significance of CEBPA mutations in children with de novo non promyelocitic AML treated in Italy with the AIEOP-LAM 2002/01 pediatric protocol. Among 205 patients enrolled in the protocol between December 2002 and December 2007, 103 were successfully analyzed for CEBPA mutations by PCR amplification of TAD and bZIP domains of the gene, and through sequencing of positive cases after DHPLC analysis. Characteristics of analyzed and non analyzed patients were not statistically different. Two types of CEBPA mutations, N-terminal (TAD) truncating mutations and in-frame bZip domain mutations, were detected in 13/103 (12.6%) patients tested; 8 of them (61.5%) harboured both mutation types.

Laboratory, clinical characteristics and outcomes for patients with CEBPA mutations were compared to those of patients with wild-type CEBPA. CEBPA mutations were significantly more common in older patients (8/13 vs 30/90 children were older than 10 years), in patients with FAB M1 (7/13 vs 4/90), and in patients with normal cytogenetics (13/13). None of the CEBPA mutated cases carried either FLT3 or NPM1 mutations. Only 1 mutated case was found in Standard Risk patients (defined as children carrying isolated CBF abnormality and achieving complete remission after 1 cycle of induction therapy), while the other 12 patients belonged to the High Risk group.

Although the values did not reach statistical significance because of the low prevalence of CEBPA mutations, with a median follow up of 39 months (range 4–86) the event-free survival probability at 5 years was 76.9% vs. 59.6% for children with or without CEBPA mutations, respectively. The values for Disease-Free Survival were 83.3% vs. 65.4% and those for Overall Survival were 90.0%. 66.4%, respectively. No difference in terms of outcome was found between patient with a single and those with double mutants, neither between those with TAD- and bZIP- mutations.

Therefore, patients in the AIEOP-LAM 2002/01 pediatric trial carrying CEBPA mutations seem to have a lower relapse rate and improved outcome, their overall survival approaching that of children belonging to the Standard Risk group (90% vs. 97%). If confirmed in a larger cohort of patients and with longer follow-up, these data suggest that CEBPA mutation analysis could be usefully employed to identify patients at lower risk of treatment failure and for allocating them into different classes of risk.