Real-World Validation of the Transplant Conditioning Intensity (TCI) Score in Allogeneic Hematopoietic Cell Transplantation: A Spanish Multicenter Study on behalf of GETH-TC

• TCI classifies transplant preparation intensity in real practice. • Higher TCI is associated with increased NRM • Intermediate TCI is linked to a decrease relapse risk • More studies are needed to assess the TCI score when younger patients are included. Background: The Transplant Conditioning Intensity (TCI) score is a novel tool aiming to stratify conditioning intensity more effectively than the existing nomenclature. TCI is predictive of early non-relapse mortality (NRM), 2-year NRM and relapse incidence (RI). Objective: We retrospectively analyzed 455 acute myeloid leukemia patients who underwent hematopoietic cell transplantation reported to Grupo Español de Trasplante Hematopoyetico y Terapia Celular (GETH). Results: Patients were classified as low (TCI 1–2, 44 %, n=200), intermediate (TCI 2.5–3.5, 36%, n=162) or high (TCI 4–6, 20%, n=93). All low‑score cases were reduced‑intensity conditioning, whereas every high‑score TCI was myeloablative. Among intermediate TCI, 97% (n=158) received a myeloablative therapy. Patients were in first complete remission in 83% (n=366) cases. Multivariate analysis revealed an increased NRM for high versus low TCI (hazard ratio [HR] 2.95; p = 0.01) and a reduced RI for intermediate versus low TCI (HR 0.62; p = 0.042). Adverse cytogenetics independently increased both NRM (HR 2.71, p=0.03) and RI (HR 2.26, p=0.006). Age > 65 years was associated with higher NRM (HR 2.72, p=0.04). Conclusion: In a real-world setting, the TCI score effectively differentiates patients by post-transplant outcomes, highlighting high TCI as a key predictor of increased NRM.