Allogeneic HSCT for classical BCR::ABL1-negative myeloproliferative neoplasms in children: the retrospective study of the EBMT Pediatric Diseases WP

Abstract This retrospective EBMT registry-based study evaluated 42 children (0.4–18 years, median 6.1) with BCR::ABL1-neg MPN (PMF, n = 33; ET, n = 3; PV, n = 1, sAML, 3; post-ET/PV-MF, n = 2) transplanted from MSD (n = 21) or non-MSD (n = 21) between 2000–2022. Conditioning was usually chemotherapy-based (n = 40; 95.2%) and myeloablative (n = 38; 92.7%). Twenty one patients received HSC from BM, 15 (36%) from PB, and 6 (14%) from CB. Day + 60 CI of neutrophil and platelet recovery was 85.7% and 78.4%. Day + 100 CI of aGvHD II-IV was 35.9% and was lower in transplanted from MSD (20% vs 52.6%, p = 0.03). Six-year CI of cGvHD was 16.6%. Six-year RI was 17.8%, PFS 64.9%, GRFS 49.1%, and OS 68.6%. Six-year RI between 2008–2022 was lower than between 2000–2007 (4.5% vs 30%, p = 0.046). In obtaining BM compared with those transplanted with HSC from BM or CB the 6-year PFS and OS was significantly higher (83.5% vs 51.4%, p = 0.04 and 80.1% vs 48.4%, p = 0.02, respectively), whereas NRM was lower (0% vs 35.3%, p = 0.004). So far, this is the largest and first one multicenter study on transplant-specific characteristics and outcomes of allo-HSCT in children with BCR::ABL1-neg MPN, which indicates need of prospective studies to establish indications for allo-HSCT and optimal transplant procedure in them.