The Simplified Comorbidity Index predicts non‐relapse mortality in reduced‐intensity conditioning allogeneic haematopoietic cell transplantation.

Summary: Comorbidity assessment before allogeneic haematopoietic cell transplantation (allo‐HCT) is essential for estimating non‐relapse mortality (NRM) risk. We previously developed the Simplified Comorbidity Index (SCI), which captures a small number of 'high‐yield' comorbidities and older age. The SCI was predictive of NRM in myeloablative CD34‐selected allo‐HCT. Here, we evaluated the SCI in a single‐centre cohort of 327 patients receiving reduced‐intensity conditioning followed by unmanipulated allografts from HLA‐matched donors. Among the SCI factors, age above 60, mild renal impairment, moderate pulmonary disease and cardiac disease were most frequent. SCI scores ranged from 0 to 8, with 39%, 20%, 20% and 21% having scores of 0–1, 2, 3 and ≥4 respectively. Corresponding cumulative incidences of 3‐year NRM were 11%, 16%, 22% and 27%; p = 0.03. In multivariable models, higher SCI scores were associated with incremental risks of all‐cause mortality and NRM. The SCI had an area under the receiver operating characteristic curve of 65.9%, 64.1% and 62.9% for predicting 1‐, 2‐ and 3‐year NRM versus 58.4%, 60.4% and 59.3% with the haematopoietic cell transplantation comorbidity index. These results demonstrate for the first time that the SCI is predictive of NRM in patients receiving allo‐HCT from HLA‐matched donors after reduced‐intensity conditioning. [ABSTRACT FROM AUTHOR]