Second allogeneic transplantation in relapsed acute leukemia - a risk worth taking?

Second allogeneic stem cell transplantation (SCT2) presents a potentially curative treatment approach in patients who relapsed after first allogeneic transplant procedure. Currently there is no consensus on second allografting. The aim of our study was to analyze the outcome and prognostic factors of SCT2 in relapsed acute leukemia setting. The study comprised 60 patients at a median age of 44.7 years (37 females, 23 males) who underwent SCT2 due to relapsed acute leukemia between 2000 and 2024 in our center. Median remission duration after SCT1 was 13.6 (IQR 30.1) months and median time from relapse to SCT2 was 4 (IQR 3) months. Disease-risk index at SCT2 was as follows: low - 2 (3.3%), intermediate - 29 (48,4%), high - 27 (45%) and very high - 2 (3.3%). The same donor was used in 52 procedures (86.7%). Six patients died before engraftment due to severe infectious complications. The 2-year probability of overall survival (OS) and leukemia free survival (LFS) were 26.6% and 26.2%, respectively. Median follow-up after SCT2 was 10.7 (IQR 35) months. At the last follow-up, 22 patients (37%) were alive. The 2-year cumulative relapse incidence (RI) was 47.4% and cumulative non-relapse mortality (NRM) was 55.3%. The factors that adversely influenced survival were as follows: early relapse after SCT1 (< 6 months after transplantation) (p = 0.018) and the use of reduced intensity conditioning before SCT2 (p = 0.0272). Presented data indicate that second allograft is a feasible option in selected patients with relapsed acute leukemia. There is still room for improvement in terms of non-relapse mortality.