Improved outcome of children with relapsed/refractory acute myeloid leukemia by addition of cladribine to re-induction chemotherapy

Background: The preferred salvage treatment for children with relapsed/refractory acute myeloid leukemia (R/R-AML) remains unclear. The combination of cladribine/Ara-C/granulocyte-colony stimulating factor and mitoxantrone (CLAG-M) shown promising results in adult R/R-AML. We aim to investigate the efficacy and safety of CLAG-M versus mitoxantrone/etoposide/cytarabine (MEC) or idarubicin/etoposide/cytarabine (IEC) in R/R-AML children.

Methods: Fifty-five R/R-AML children were analyzed. The overall response rate (ORR), overall survival (OS), and progression-free survival (PFS) at 3-year were documented. Karyotype or mutations status were summarized as different risk groups.

Results: The ORR was achieved in 80% (16/20) and 51% (18/35) of patients after one-cycle of CLAG-M and MEC/IEC treatment (p < 0.001). The CLAG-M group’s OS (66.8% ± 16.2% vs. 40.4% ± 10.9%, p = 0.019) and PFS (52.6% ± 13.7% vs. 34.9% ± 9.1%, p = 0.036) at 3-year was significantly higher than the MEC/IEC group. In high-risk patients, 33.3% experienced progression of disease (PD) and 22.2% dead in CLAG-M group, while 50% experienced PD and 43.8% dead in MEC/IEC. When it comes to low-risk group, none of them in CLAG-M experienced PD or death, while up to 50% of patients received MEC/IEC suffered PD, and all of them died eventually. Similar results were also found in the intermediate-risk group. Surprisingly, the presence of FLT3-ITD was associated with poor outcome in both groups. The most common adverse events were hematologic toxicities, and the incidence was similar in both group.

Conclusions: CLAG-M group demonstrated effective palliation along with acceptable toxicity in R/R-AML patients. However, patients with FLT3-ITD may benefit less from CLAG-M, owing to higher PD rate and all-cause mortality than other patients.