PB1717 RELAPSES OF CHILDHOOD MYELOID LEUKEMIA, A CASE SERIES
Authors: M. Nikita, M. Servitzoglou, A. Pourtsidis, D. Doganis, K. Kapetaniou, S. Papachristidou, E. Magkou, T. Anastasiou, M. Baka
Journal: HemaSphere (2019)

Background: Despite significant progress in treating paediatric acute myeloid leukaemia (AML), relapse rates still range between 30% and 40%, with overall survival rates commonly below 70%. Aims: The aim of this study is the identification of all relevant characteristics and outcomes in a group of patients with childhood AML who relapsed after initial diagnosis or after bone marrow transplantation (BMT) in our department. Methods: All children diagnosed with a first relapse of AML in our Department, from January 1996 till December 2015 were included in this study. Results: During this period, a total number of 74 patients with childhood AML were treated in our Department, according to BFM protocols. Recurrence occurred in 24 patients (32,5%, 10 male – 14 female - median age: 5,9 years), within 3 to 50 months from initial diagnosis. According to FAB classification 3 children were M0, 2 M1, 3 M2, 1 M3, 5 M4, 5 M5 and 5 M7. 6 patients had also central nervous system (C.N.S) infiltration and only one had testicular infiltration. The mean WBC, Hb, Blasts and PLT values at diagnosis were 27300/mm3, 8,3 g/dl, 21360/mm3 and 36500/mm3, respectively. Regarding cytogenetic characteristics of the patients at diagnosis, 6 of them had normal karyotype with one having MLL rearrangement. Also 3 patients had MLL rearrangement with complex karyotype, two with r(6), one with t(8;21) translocation, one with del(6), one with del(7) and one with trisomia 13. First remission (CR1) after the induction therapy was achieved in 19 children, while 5 received more chemotherapeutic agents. Finally four patients were classified as low risk and 20 as high risk. In 21 patients recurrence involved the bone marrow, in 4 both bone marrow and CNS and in 3 isolated CNS. Seven children (29%) had received allogeneic BMT from a matched related donor in first complete remission (CR1) and relapsed 5-29 months from initial diagnosis and 17 children had received conventional chemotherapy and relapsed 3-50 months from initial diagnosis too. Five patients are still alive and well 23, 45, 57, 145 and 163 months after initial diagnosis. The first two children relapsed in bone marrow and they are in CR2 after BMT. The third and the forth relapsed in CNS and they are in CR2 with conventional chemotherapy. The fifth initially relapsed in bone marrow and achieved CR2 with BMT. However he had a second relapsed both bone marrow and CNS and he is in CR3 after second BMT. The first and the fifth children were classified as low risk. 19 children died 3-53 months after initial diagnosis. 7 relapsed after BMT in CR1 and six of them died from disease progression with or no severe infection and one due toxicity within 5-29 months. Out of the other 12 children, 7 achieved CR2 with BMT but they died due to disease progression within 8-38 months. Nevertheless, five out of the twelve children died due to disease progression within 3-51 months. Summary/Conclusion: The overall survival rate in children with relapsed acute myeloid leukemia is low. The prognosis is worse in children with bone marrow relapse than others with isolated CNS relapse. The development of new classes of innovative drugs or immunotherapy is required to enhance response and improve the overall survival.