Experience with second allogeneic hematopoietic stem cell transplantation in Chilean patients: A single-center study.

INTRODUCTION: Allogeneic hematopoietic stem cell transplantation is potentially a curative treatment for several hematological diseases. However, post-transplant relapse remains a significant challenge. For patients who achieve a second complete remission, a second allogeneic transplantation may be a promising therapeutic option. The aim of this study was to analyze clinical outcomes including graft-versus-host disease, non-relapse mortality, and relapse rates, as well as graft sources in patients who underwent a second allogeneic transplantation in a university-based transplant program. PATIENTS AND METHODS: A retrospective analysis of 21 adult patients who underwent a second allogeneic transplantation between 2001 and 2023 was performed. Data on demographics, underlying disease, graft source, conditioning, graft-versus-host disease, relapse, and survival were collected. Survival estimates were calculated using the Kaplan-Meier method. RESULTS: The graft source was bone marrow in 60 % and peripheral blood in 40 % of cases. Grade III-IV acute graft-versus-host disease occurred in 5 % and extensive chronic graft-versus-host disease in 17 %. The non-relapse mortality was 69.2 %, and disease relapse occurred in 23.1 %. The one-year progression-free survival was 26.5 %, and overall survival was 42.3 %. Compared to those transplanted before 2010, patients who underwent transplantation after 2010 showed improved two-year PFS and OS, reaching 55 % and 45.4 %, respectively. CONCLUSION: A second allogeneic transplantation may offer a survival benefit in selected patients with relapsed hematologic malignancies or bone marrow failure syndromes. Despite high non-relapse mortality, outcomes have improved in recent years with better salvage strategies.