Improved Outcomes after Allogenic Hematopoietic Stem Cell Transplantation with Fludarabine/Treosulfan for Patients with Myelodysplastic Syndromes

While allogeneic hematopoietic stem cell transplantation (allo-HCT) currently offers the only curative option for patients with myelodysplastic syndrome (MDS), there is still a high risk of relapse or transplant-related complications. We collected data on all patients who had undergone allo-HCT at our center (Copenhagen University Hospital) between 2000 and 2018. In total, 215 patients with MDS (n = 196) or chronic myelomonocytic leukemia (n = 19) were included. Estimated 1-year overall survival (OS) was 70.3% (95% confidence interval [CI], 64.2% to 77.0%), and the median survival was 7.7 years (95% CI, 4.7 to indeterminable). There was a significant improvement in OS over time (P = .011, comparing 2000 to 2010, 2010 to 2014, and 2014 to 2018). Treatment was standardized throughout the study period, allowing comparison between patients receiving nonmyeloablative (NMA, n = 124), standard myeloablative (SMA, n = 36), and fludarabine and treosulfan (FluTreo, n = 55) conditioning. FluTreo has myeloablative properties but lower toxicity and replaced standard myeloablative conditioning at our center in 2014. The FluTreo group was significantly older and had more comorbidities than the SMA group but similar disease severity. One-year OS was 84.0% (95% CI, 74.3% to 94.9%), 58.3% (95% CI, 44.3% to 76.9%), and 68.3% (95% CI, 60.2% to 77.5%) for FluTreo, SMA, and NMA, respectively (P = .04). In univariate analysis, Revised International Scoring System (IPSS-R) (high versus low), donor sex mismatch, and cytomegalovirus status mismatch were significant factors for OS. In multivariate analysis of OS including age, IPSS-R, and HCT specific comorbidity index, NMA was borderline inferior to FluTreo (P = .073) while SMA was significantly inferior to FluTreo with a hazard ratio of 6.89 (95% CI, 2.53 to 18.77, P < .001). The introduction of FluTreo allowed us to administer a myeloablative regimen to a broader patient group and shows promising results.