Acute myelocytic leukemia (AML) in Down Syndrome (DS) children is characterized by a young age of onset (< 2 years), a low white blood cell count and high frequency of Megakaryocytic leukemia. DS children with AML have higher disease free survival (DFS) rates as compared to non DS AML patients. Previous studies have suggested that intensification chemotherapy may not be necessary for the treatment of DS children with AML. The objective of this study was to clarify the effectiveness and toxicities of using high dose Cytosine Arabinoside (HD AraC) intensification in the treatment of DS AML. Clinical data for children (<14 years) with DS AML, diagnosed between September 2000 to May 2005, were retrieved from the hospital data base. Patients were divided into two groups; Group A patients received chemotherapy containing HD AraC, while Group B patients did not. A total of 15 patients were included, eight in Group A and seven in group B. The median age at diagnosis was 22 months (A=23 months, B=22 months). The two groups were matched regarding their clinical and laboratory parameters. There was no significant difference in DFS between groups A and B, 75% and 85% respectively (P = 0.82) at a mean observation period of 42.9 months for group A and 23.12 months for group B. The median time to relapse was 6 months for group A and 8 months for group B. The overall treatment related toxicity was higher in Group A patients but achieved only borderline significance (P = 0.06). However, when toxicity was assessed separately for induction and post induction phases of chemotherapy there were significantly more infectious events (17 v. 2; p=0.0006) in the post induction phase which includes HD AraC intensification in Group A. Even when only serious infections (bacteremia, fungal infection, sepsis) were included in the evaluation this difference persisted (7 v. 1; p=0.0339), with less toxicity for Group B patients. No such difference was noted between the two groups during induction chemotherapy. In conclusion the use of HD AraC in post-induction intensification phases for DS AML children does not improve DFS and is associated with more treatment related toxicity.

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