Conditioning intensity in myelodysplastic patients aged ≥ 50 years undergoing allogeneic hematopoietic cell transplantation (allo-HCT): a study on behalf of the chronic malignancies working party of the EBMT.

Reduced intensity conditioning (RIC) is usually used for patients with myelodysplastic syndrome (MDS) undergoing allogeneic hematopoietic cell transplantation (allo-HCT), particularly in the elderly or those with comorbidities. The impact of conditioning intensity on patients' outcome remains controversial with clinicians' subjective opinion/ experience remaining a major guide in choosing the intensity. Here, we compare RIC versus MAC in a large EBMT retrospective study in MDS patients aged ≥50 years undergoing allo-HCT between 2014 and 2018. Among the 1393 included patients, 922 (66%) were males, and the median age at transplant was 62.8 (50.0-77.9) years. The majority of patients (n = 884; 64.3%) had MDS with excess blasts. IPSS-R recorded was very low/low (n = 598, 43%), intermediate (n = 352, 25%), and high/very high (n = 443, 32%). Karnofsky index was ≥90 in 916 (69.3%) patients, and HCT-CI ≥ 3 in 292(27.3%) patients. A RIC regimen was used in 1053 (75.5%) patients. Median follow-up was 27.9 months (IQR: 26.4-30.6). Both uni- and multi-variable analyses did not show any significant association between conditioning intensity and outcomes. This study highlights a lack of association between RIC/MAC regimens and outcomes in allo-HCT MDS patients. Our results support the recently published systematic review and meta-analysis, where evidence for using one conditioning regimen over another remains weak.