Allogeneic Hematopoietic Cell Transplantation in Advanced Systemic Mastocytosis: A retrospective analysis of the DRST and GREM registries

We identified 71 patients with AdvSM (aggressive SM [ASM], SM with an associated hematologic neoplasm [SM-AHN, e.g., acute myeloid leukemia, SM-AML], mast cell leukemia [MCL]) in two national registries (DRST/GREM) who received an allogeneic hematopoietic cell transplantation (alloHCT) performed in Germany from 1999–2021. Median overall survival (OS) of ASM/SM-AHN ( n = 30, 45%), SM-AML ( n = 28, 39%) and MCL ± AHN ( n = 13, 19%) was 9.0, 3.3 and 0.9 years ( P = 0.007). Improved median OS was associated with response of SM (17/41, 41%; HR 0.4 [0.2–0.9], P = 0.035) and/or of AHN (26/43, 60%, HR 0.3 [0.1–0.7], P = 0.004) prior to alloHCT. Adverse predictors for OS included absence of KIT D816V (10/61, 16%, HR 2.9 [1.2–6.5], P