Outcomes and risk factors of second allogeneic haematopoietic stem cell transplantation in patients with relapsed haematological malignancy after first transplantation.

The therapeutic utility of a second allogeneic haematopoietic stem cell transplantation (allo-HSCT) remains uncertain in patients with relapsed haematological malignancies following initial allo-HSCT. This retrospective cohort study analysed 58 consecutive patients undergoing second allo-HSCT, predominantly haploidentical, to determine indications and identify predictive factors. All evaluable patients achieved successful and sustained haematopoietic reconstitution, with confirmed complete donor chimerism. As of the data cut-off, two patients died at 1.3 and 2 months post second transplantation with persistent non-response (NR). Twelve of the remaining 56 patients relapsed after the second transplantation, with a median relapse time of 5.5 (3.0-13.5) months. One-year overall survival (OS), disease-free survival and cumulative incidence of relapse rates after the second transplant were 52.1%, 46.5% and 21.8% respectively. Treatment-related mortality (TRM) following the second transplant was 5.3% and 31.9% at 3 months and 1 year respectively. Age >55 and/or HCT-CI ≥3 and short initial remission duration (≤8 months) contributed to significantly inferior OS and higher TRM. This study implemented a strategy combining donor switching and post-transplant maintenance therapy for second transplantation in haematological malignancy patients with post-transplant relapse. Prospective studies are warranted to validate prognostic factors affecting outcomes after second transplantation.