Low dose pre-transplant splenic radiotherapy for myeloproliferative neoplasms

Splenic radiotherapy (SRT) may be used in combination with allogeneic hematopoietic stem cell transplantation (Allo-HSCT) to improve symptoms and sequestration related to splenomegaly for patients with myelofibrosis (MF). We describe treatment outcomes and safety of low dose SRT (LDSRT) prior to reduced intensity conditioning (RIC) allo-HSCT in patients with MF between 2017–2023 at a single institution. Thirty-five patients underwent RIC consisting of fludarabine/melphalan in preparation for allo-HSCT. Seventeen patients with persistent splenomegaly after ruxolitinib treatment completed LDSRT (most often 5 Gy in 5 consecutive daily fractions). Engraftment success (LDSRT 94.1% vs no LDSRT 94.4% p = 1.0), neutrophil recovery (LDSRT: 18 days vs no LDSRT 17 days, p = 0.437), overall survival, and relapse free survival were similar between both groups despite higher rates of ruxolitinib-resistance (p = 0.001) and splenomegaly (p = 0.001) in the LDSRT cohort. LDSRT is feasible and safe in combination with RIC allo-HSCT without compromising transplant related outcomes.