DP107 | MONITORING OF MINIMAL RESIDUAL DISEASE ON PERIPHERAL BLOOD IN THE POST-TRANSPLANT PERIOD ALLOWS AVOIDANCE OF REPEATED BONE MARROW ASPIRATIONS IN PATIENTS WITH ACUTE MYELOID LEUKEMIA

Acute myeloid leukemia (AML) requires strict monitoring of minimal residual disease (MRD). We aimed to explore if MRD monitoring on peripheral blood (PB) represents a valid and less invasive alternative to repeated bone marrow (BM) aspirates in adults with AML undergoing allogeneic hematopoietic stem cell transplantation (HSCT) at Federico II University Hospital in Naples. Molecular markers to follow on PB included NPM1, WT1, CBF-AML, BCR-ABL, and PML-RARA. MRD positivity or biochemical/clinical suspicion of disease relapse prompted to BM aspirate. Forty-one patients (17 males and 24 females) underwent HSCT for AML between July 2020 and November 2024. Median age at transplant was 58 (range 30-72) years. MRD monitoring post-transplant was performed using NPM1 in 18, WT1 in 18, CBF-AML in 2, BCR-ABL in 2 and PML-RARA in 1 patient. Disease status at transplant was CR1 in 25, CR2 in 10 (including 6 with MRD+ at transplant) and active disease in 6 patients. Conditioning regimen was myeloablative, reduced-intensity or sequential in 20, 14 and 7 patients, respectively. Stem cell source was BM in 12 and PB in 29 cases. Donors were HLA-identical in 11, matched unrelated in 21, haploidentical in 9 cases. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine associated to mycophenolate mofetil (n=29) or methotrexate (n=12). ATG or PTCY were also used in 27 and 11 patients, respectively, while 3 received both. All patients achieved neutrophil engraftment with a median time of 14 (range 8-23) days. All but one patient achieved platelet engraftment with a median time of 14 (range 8-34) days. Grade II-IV acute GVHD occurred in 6 while chronic GVHD in 8 patients (mild, n=5; moderate, n=2; extensive, n=1). MRD positivity during follow-up was detected in 10 cases, with 3 contextual overt relapses on BM and one occurring one month later. Preemptive treatments were introduced in 6 cases. Later on, 2 patients experienced overt hematological relapse 15 and 12 months from previous molecular relapse while one patient experienced extramedullary relapse. Preemptive treatments were used in 6 cases, prophylactic treatments were used in 4, while 7 patients were treated for overt relapse. With a median follow-up of 23 (range 5-57) months, 2-year PFS and OS were 67±9% and 85±6%. In our experience, MRD monitoring using PB represented a sensitive strategy to detect molecular or overt relapse avoiding repeated bone marrow aspirations during the follow-up.