Adjusting Disease Risk Index for Regional Variations and Donor Selection

The Disease Risk Index (DRI) is a widely used prognostic tool following hematopoietic stem cell transplantation (HSCT), based on disease classification and status. However, the refined DRI (rDRI) does not fully account for regional variations in disease distribution and treatment practices. To refine the rDRI by accounting for underrepresented disease entities in the rDRI and by considering regional differences in HSCT treatment strategies, and to identify the most suitable donor selection strategy based on the newly developed disease risk criteria. We analyzed 7720 patients with hematologic malignancies who underwent their first allogeneic HSCT between 2014 and 2016 and developed a region-adjusted DRI (raDRI) using the Japanese registry database. We then validated predictive performance in 5108 patients transplanted between 2017 and 2018. The raDRI demonstrated superior accuracy compared with the rDRI (time-dependent AUC: .705 versus .670; integrated calibration index: .016 versus .017). In patients with low to intermediate raDRI, matched related donors (MRD) were associated with improved overall survival compared with matched unrelated bone marrow donors (bone marrow (BM): hazard ratio (HR) .50, 95% CI: .26 to .96; peripheral blood (PB): HR .54, 95% CI: .36 to .83), whereas no differences were seen in patients with high to very high raDRI (MRD-BM: HR: 1.03, 95% CI: .69 to 1.54, MRD-PB: 1.15, 95% CI: .89 to 1.49). Our findings underscore that prognostic indices such as the DRI are inherently shaped by the populations and clinical practices from which they are derived. Regional differences in disease prevalence, treatment strategies, and donor-source utilization can substantially influence risk stratification and transplant outcomes.