[Preventive and therapeutic strategies for relapse after hematopoietic stem cell transplant for pediatric AML (SFGM-TC)]. / Stratégies préventives et thérapeutiques de la rechute après allogreffe de cellules souches hématopoïétiques pour les LAM pédiatriques (SFGM-TC).

Treatment of pediatric high-risk acute myeloid leukemia (AML), defined either on molecular or cytogenetic features, relies on bone marrow transplant after cytologic remission. However, relapse remains the first post-transplant cause of mortality. In this 13th session of practice harmonization of the francophone society of bone marrow transplantation and cellular therapy (SFGM-TC), our group worked on recommendations regarding the management of post-transplant relapse in AML pediatric patients based on international literature, national survey and expert opinion. Overall, immunomodulation strategy relying on both measurable residual disease (MRD) and chimerism evaluation should be used for high-risk AML. In very high-risk (VHR) AML with a 5-year overall survival ≤30 %, a post-transplant maintenance should be proposed using either hypomethylating agents, combined with DLI whenever possible, or FLT3 tyrosine kinase inhibitors if this target is present on leukemia cells. In the pre-emptive or early relapse settings (< 6 months post-transplant), treatments combining DLI, Azacytidine and Venetoclax should be considered. Access to phase I/II trails for targeted therapies (menin, IDH or JAK inhibitors) should be discussed in each patient according to the underlying molecular abnormalities of the disease.

Prediction of success of CD34+ collection for autotransplantation in children.

INTRODUCTION: Intensive chemotherapy with autologous stem cell transplantation is a therapeutic tool used in paediatric oncology. In adult patients, a peripheral blood CD34+ cell count superior to 20/µL enables an adequate collection of peripheral blood stem cells. There are no recommendations for children. This study aimed to determine whether the count of circulating CD34+ cells on the day before cytapheresis predicts successful collection in paediatric patients. METHODS: We retrospectively studied all paediatric patients who underwent apheresis for stem cell autotransplantation in the CHU of Rennes between 2010 and 2019. Successful apheresis was defined as a collection superior to 3×106 CD34+/kg. "Success" and "failure" groups were compared. RESULTS: In total, 122 apheresis procedures were performed in 105 patients. It was a successful procedure in 81% of patients and a failure in 19% of patients. A minimal cut-off of circulating CD34+ count superior to 13/µL on D-1 allowed us to predict a collection of at least 3×106 CD34+/kg (PPV 94,8%, NPV 51,4%). For children aged<6 years, the association with leucocyte increase during the 5 days before the procedure improved the prediction of success. DISCUSSION: The peripheral blood CD34+ cell count is a predictive factor for successful collection in paediatric patients. The minimal cut-off that allows an adequate collection of peripheral blood stem cells is inferior to the minimal cut-off in adult patients. Nevertheless, this minimal number of circulating CD34+ cells is insufficient to predict the success or failure of apheresis in patients younger than 6 years of age.