Comorbidities in recipients of low transplant conditioning intensity regimens for acute myeloid leukemia: an ALWP EBMT study.

Older age and high burden of comorbidities often drive selection of low-intensity conditioning regimens in allogeneic-hematopoietic stem cell transplantation (HSCT) recipients. However, the impact of comorbidities in the low-intensity conditioning setting is unclear. We sought to determine the contribution of individual comorbidities and their cumulative burden on the risk of non-relapse mortality (NRM) in patients receiving low-intensity regimens. In a retrospective analysis of adults (≥ 18 years) transplanted for acute myeloid leukemia (AML) in first complete remission (CR) between 2008-2018, we studied recipients of low-intensity regimens as defined by the Transplantation Conditioning Intensity (TCI) scale. Multivariable Cox models were constructed to study associations of comorbidities with NRM. Comorbidities identified as putative risk factors in the low-TCI setting were included in combined multivariable regression models assessed for overall survival, NRM, and relapse. A total of 1,663 patients with a median age of 61 years received low-TCI regimens. Cardiac comorbidity (including arrhythmia/valvular disease) and psychiatric disease were associated with increased NRM risk (hazard ratio [HR] 1.54 [95% CI 1.13, 2.09] and 1.69 [1.02, 2.82], respectively). Moderate pulmonary dysfunction, though prevalent, was not associated with increased NRM. In a combined model, cardiac, psychiatric, renal, and inflammatory bowel disease were independently associated with adverse transplantation outcomes. These findings may inform patient and regimen selection and reinforce the need for further investigation of cardioprotective transplantation approaches.