Is the New Tci Score Sufficient to Categorize the Intensity of Conditioning? a Single-Centre Study

Introduction The Transplant Conditioning Intensity (TCI) score provides a more precise evaluation of conditioning intensity than the classical myeloablative (MAC) and reduced-intensity (RIC) stratification. Objectives The primary objective of this study was to ascertain if the TCI score can stratify the overall survival (OS), regardless of donor type; secondary objectives were transplant-related mortality (TRM), graft-versus-host disease-relapse free survival (GRFS) according to the different TCI categories. Methods Herein we report the outcomes of 556 patients who underwent transplantation at Spedali Civili (Brescia-Italy) from 2006 to 2023, including haploidentical and cord blood recipients. The indication to transplant was: 40% acute myeloid leukemia, 7% myelodysplastic syndrome, acute lymphoblastic leukemia 14%, non-Hodgkin lymphoma 8%, Hodgkin lymphoma 6%, chronic myeloid leukemia 2%, chronic lymphocytic leukemia 3%, multiple myeloma 8%, aplastic anemia 2%, cutaneous lymphoma 1%, myeloproliferative neoplasm 8%, others 1%. Thirty-eight% were females and sixty-two% were males. Median age was 53 years (16 - 75). Median follow up was 22 months (1 - 215). Donor categories were matched sibling (34%), unrelated (46%), haploidentical (18%) and umbilical cord blood (2%). MAC and RIC regimens were used in 47% and 53% of patients, respectively. TCI scores were: 36% low, 37% intermediate and 22% high. MAC and high TCI were more prevalent among younger patients with lower comorbidities, Karnofsky > 80 and not in first complete remission (CR1). Results The TCI score was able to predict OS (p<0.001) and GRFS (p=0.002), both in the entire cohort and in patients aged ≥ 50 years. Cumulative incidence of TRM (p =0.23) did not significantly differ across TCI categories. There was no difference in cumulative incidence of relapse across the different TCI categories; this is likely consequence of a higher prevalence of not-CR1 diseases within the high TCI subgroup. Cumulative incidence of acute GVHD was higher in high TCI patients; the risk of chronic GvHD did not differ between the different TCI categories. In the intermediate TCI group(currently missed by the current MAC/RIC classification), patients aged ≥ 50 years were 65% and 60% had disease not in CR1. The Disease Risk Index (DRI) within the intermediate TCI showed, 66% low to intermediate and 32% as high and very high, respectively. OS (p=0.048) and GRFS (p=0.0005) were lower in patients with a high DRI, with relapse being the main cause of treatment failure. Conclusion The TCI index can predict OS and GRFS regardless of donor type, particularly in patients over 50 years. The intermediate group can be further stratified according to the DRI, identifying patients needing strategies to mitigate the risk of relapse. Future studies are needed to include alternative donors, patients’ age and fitness, and disease characteristics within the TCI index.