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The treatment of relapsed/refractory (R/R) acute myeloid leukaemia (AML) remains a challenge. Among salvage chemotherapy regimens, the clofarabine and cytarabine (CLARA) combination has been widely evaluated and has a favourable safety/efficacy balance. Predictive factors of efficacy in patients with R/R AML are unclear, particularly the impact of AML-related gene mutations. We report our single-centre experience on 34 R/R AML patients treated with CLARA, with a focus on the genetic characterization of our cohort. CLARA yielded a 47% response rate among this poor-prognosis AML population, while two patients (5·8%) died due to treatment-related toxicity. The two-year progression-free survival and overall survival rates were 29·4% and 35·3%, respectively. Nine patients (26%) had long-term response with a median follow-up of 39·5 months among the responders, of whom six underwent haematopoietic stem cell transplantation. Adverse karyotype did not correlate with response or survival, and secondary AML were more frequent among responders to CLARA, suggesting that this combination may successfully salvage R/R AML patients regardless of adverse prognostic markers. We also observed that a low mutational burden and absence of splice mutations correlated with prolonged survival after CLARA, suggesting that extensive genotyping may have prognostic implications in R/R AML.

Background Compelling evidence has emerged for the relevance of flow cytometry (FC) in the diagnostic work-up of myelodysplastic syndromes (MDS) but due to technical issues, the erythroid lineage has been under investigated, specifically in the therapeutic context. Methods Using the "no red cell lysis" method developed to set up the RED-score, we specifically quantified the fraction of CD117/c-KIT-expressing erythroid precursors in a cohort of 144 MDS patients and studied the correlation with response to erythropoiesis-stimulating agents (ESA) in a sub cohort of 63 low-risk MDS patients. Results We confirmed the previously reported increase in CD117/c-KIT-expressing erythroid precursors in a subset of MDS patients and demonstrated a strong association between a cut off of CD117/c-KIT-expressing erythroid precursors ≥3% and ESA response (P = 0.001), independent of red blood cell requirement. From our observations, we hypothesized that a decrease in CD117/c-KIT-expressing erythroid precursors could be a mechanism of ESA failure. Moreover, the fraction of CD117/c-KIT-expressing erythroid precursors was correlated with progression-free survival in low-risk MDS patients (P = 0.018). In vitro, we demonstrated in an EPO dependent cell line that CD117/c-KIT expression is necessary for cell survival under EPO stimulation. Conclusions The quantification of the CD117/c-KIT-expressing erythroid precursors could be proposed as a new theranostic and prognostic marker in MDS treated by ESA. Future studies will be required to determine whether modulating CD117/c-KIT expression and signaling could be used to improve anemia in MDS. © 2019 International Clinical Cytometry Society.