For a study, researchers sought to put together a retrospective cohort of chronic myelomonocytic leukemia (CMML) patients 18–70 years diagnosed between 2000 and 2014 from an international CMML dataset (n = 730) and the EBMT registry (n = 384) to assess the survival benefit of allogeneic hematopoietic cell transplantation (allo-HCT) in CMML.

Age, sex, CMML prognostic scoring system (low or intermediate-1 grouped as lower-risk, intermediate-2 or high as higher-risk) at diagnosis, and AML transformation were taken into account when analyzing the prognostic impact of allo-HCT using univariable and multivariable time-dependent models as well as a multistate model. With allo-HCT, lower-risk CMMLs had a 5-year overall survival (OS) of 20% compared to 42% without allo-HCT (P<.001) in univariable analysis. With allo-HCT, 5-year OS was 27% in individuals at greater risk than 15% without allo-HCT (P=.13).

Allo-HCT before AML transformation decreased OS in patients with lower-risk CMML according to multistate models. Still, it was projected to improve survival for males with higher-risk CMML. Allo-HCT performed before transformation to AML significantly increased the risk of death within 2 years of transplantation (hazard ratio [HR], 3.19; P<.001); however, there was no significant difference in long-term survival beyond this time point (HR, 0.98; P=.92) in a multivariable analysis of lower-risk patients. Allo-HCT substantially increased the risk of mortality in higher-risk patients during the first two years following transplantation (HR 1.46; P=.01) but not after that (HR 0.60; P=.09).

Allo-HCT before AML transformation reduced life expectancy in people at lower risk, but it may be an option for patients at higher risk.