Impact of Pre-Graft Ruxolitinib on Post-Transplantation Outcome in Myelofibrosis Patients

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative therapy in patients with primary or secondary myelofibrosis. Ruxolitinib, a JAK-inhibitor, has been approved in myelofibrosis patients and is effective to alleviate symptoms of the disease in a substantial proportion of patients. In a French phase 2 study, the use of ruxolitinib as a bridge to HSCT was followed by a high transplantation rate, with one third of patients presenting clinical improvement before HSCT (partial response or spleen size reduction) (BMT 2021, Robin et al). The aim of the current study is to compare post-transplantation outcomes between patients who received ruxolitinib before HSCT and those who did not. Methods: This retrospective study includes patients with primary or secondary myelofibrosis registered in the SFGM-TC registry including patients from France, Belgium and Switzerland. Patients who received HSCT between July 2010 and December 2019 with available information regarding ruxolitinib treatment were included. The impact of ruxolitinib was analyzed by multivariable Cox regression and a propensity score. Results: 305 patients could be included, of whom 143 received ruxolitinib prior to HSCT (RuxoG). All patient characteristics are given in RuxoG followed by no ruxolitinib group (noRuxo). The diagnosis before HSCT was primary myelofibrosis (83% vs 75%), secondary myelofibrosis (13% vs 19%) or transformed into AML (4% vs 6%). Karnofsky score at transplant was < 70% in 9% and 11%. In RuxoG. median age was older (60.29 vs. 58.75, p=0.069) and delay from diagnosis longer (20.42 vs 13.26 months, p=0.040). RuxoG patients had less frequently anemia < 10 g/dl (84% vs 98%, p=0.027) or thrombocytopenia < 50 G/L (22% vs 32%, p=0.066) and presented more frequently splenomegaly or pre-graft splenectomy (83% vs 63%, p=0.0007). DIPSS score was well balanced in both groups, being high or intermediate-2 in 100 patients (79% vs 86%, p=0.23), from the 235 patients with available data. Myeloablative conditioning regimen was used in 16% vs 26% (p=0.049), and conditioning regimen consisted of on fludarabine-busulfan in 33% vs 61%, fludarabine-melphalan in 47% vs 22% or other in 20% vs 16% (p