Impact of Post-Transplant Cyclophosphamide on the Prognostic Value of HCT-CI.

The hematopoietic cell transplant comorbidity index (HCT-CI) is a validated prognostic tool for baseline assessment in allogeneic hematopoietic cell transplantation (HCT). The impact of the individual components of the HCT-CI on prognosis remains unknown for patients undergoing post-transplant cyclophosphamide (PTCY) based graft versus host disease (GVHD) prophylaxis. Data were collected and validated from patients undergoing HCT for myelodysplastic syndrome or acute myeloid leukemia at our center between 2018 and 2022. Multivariable regression analysis was used to identify an optimized subset of HCT-CI; Akaike information index (AIC) was used to assess model fit; C-index was used to evaluate the predictive ability of models. From 586, 184 (31%) received PTCY; HCT-CI comorbidities were balanced between non-PTCY and PTCY- subgroups except for renal, which was only present in 8 patients. Higher HCT-CI was associated with an increased cumulative incidence of NRM in univariable (3-year NRM: 22% [≥5] versus 12% [2 to 4] versus 4.8% [0 to 1], P = .0002) and multivariable analysis (subdistribution HR 4.28 for HCT-CI ≥5, P = .0003, 2.61 for 2 to 4, P = .013). Subset of HCT-CI comorbidities-diabetes, infection, peptic ulcer disease, renal, rheumatologic, and severe pulmonary comorbidities- had a similar impact on NRM as the total score. Diabetes and cardiac comorbidities had a strong association with NRM, and the addition of cardiac comorbidities improved the C-index only in the PTCY subgroup. The HCT-CI retains prognostic significance in the PTCY era, although refinement may be required. Future studies can identify links between cardiac comorbidities and NRM when using PTCY.