仲宗根 秀樹

Using data from a nationwide Japanese registry, we evaluated the impact of the total body irradiation (TBI) dose in reduced-intensity conditioning (RIC) for allogeneic hematopoietic cell transplantation (allo-HCT) in patients with acute myeloid leukemia (AML). Adults undergoing their first allo-HCT with RIC between 2010 and 2021 were classified into three groups: non-TBI, low-TBI (2 to < 4 Gy), or moderate-TBI (4-8 Gy). Outcomes were analyzed separately for patients in complete remission (CR, n = 1949) and those in the non-CR group (n = 1484). Non-TBI was associated with higher overall mortality than low-TBI (hazard ratio [HR], 1.27; 95% confidence interval [CI], 1.03-1.56 in CR; HR, 1.19; 95% CI, 1.00-1.42 in non-CR). Moderate-TBI showed no significant difference in overall mortality compared to low-TBI (HR, 0.96; 95% CI, 0.80-1.15 in CR; HR, 0.89; 95% CI, 0.77-1.05 in non-CR). Among patients in the CR group with matched sibling donors, moderate-TBI reduced overall mortality (HR, 0.33; 95% CI, 0.17-0.64) and relapse (HR, 0.29; 95% CI, 0.12-0.69). In cord blood transplantation, non-TBI increased relapse in CR (HR, 2.73; 95% CI, 1.48-5.06) and overall mortality in non-CR (HR, 1.62; 95% CI, 1.19-2.19). In haploidentical transplants, non-TBI increased relapse (HR, 5.52; 95% CI, 1.72-17.72 in CR; HR, 1.54; 95% CI, 1.04-2.30 in non-CR). The incidence of secondary primary malignancies did not differ according to the use or dose of TBI. In conclusion, adding low- or moderate-TBI to RIC may improve disease control and survival without increasing non-relapse mortality.

Choosing an optimal alternative donor is an important clinical concern in allogeneic hematopoietic cell transplantation (HCT). In Japan, single-unit umbilical cord blood transplantation (UCBT) has been widely used in the last two decades, whereas HCT from HLA-haploidentical related donors (haplo-HCT) has been increasingly used following the advent of posttransplant cyclophosphamide (PTCY) for graft-versus-host disease (GVHD) prophylaxis. This registry-based study aimed to compare outcomes between single-unit UCBT (n = 848) and PTCY-based haplo-HCT (n = 241) performed during first complete remission in patients with acute myeloid leukemia. UCBT was associated with a lower likelihood of engraftment (P < 0.001), a higher risk of grade 2-4 and grade 3-4 acute GVHD (P = 0.003 each), and a lower risk of extensive chronic GVHD (P = 0.048). The UCBT and haplo-HCT groups did not significantly differ in 3-year probabilities of overall survival (68% versus 69%, P = 0.686), GVHD/relapse-free survival (55% versus 54%, P = 0.866), relapse (14% versus 16%, P = 0.463), and non-relapse mortality (21% versus 19%, P = 0.403), respectively, which were confirmed with multivariate analysis. These results indicate that both procedures should be considered viable options for patients lacking a matched donor.

In this Japanese registry-based analysis of 9105 adult patients with acute leukemia undergoing allogeneic hematopoietic stem cell transplantation, a marked difference in survival was observed based on platelet levels: ≤ 20 × 109/L, 20-50 × 109/L, and > 50 × 109/L. The number of patients with thrombocytopenia receiving cord blood (CB, 39%) was significantly larger than those receiving unrelated bone marrow (uBM, 17%) on Day 50 (p < 0.001); however, this difference disappeared on Day 100 posttransplantation (both 11%, p = 0.4).

Pre-engraftment syndrome (PES) is a unique complication of cord blood transplantation (CBT) whose risk factors and impact on transplant outcomes remain controversial. Using a nationwide database in Japan, we analyzed a total of 3734 patients who underwent single-unit CBT. PES occurred in 18.3% of patients, and risk factors for PES included a higher hematopoietic cell transplantation-specific comorbidity index, first transplantation, myeloablative conditioning (MAC), lower total nucleated cell (TNC) dose, and graft-versus-host disease (GVHD) prophylaxis regimens excluding tacrolimus with methotrexate. Patients who developed PES had significantly higher incidences of grade II-IV acute GVHD (53.1% vs. 31.3%, p < 0.001) and chronic GVHD (27.2% vs. 21.7%, p = 0.002) compared to those without PES. Landmark analysis with multivariable adjustment revealed that PES was independently associated with increased non-relapse mortality (NRM, hazard ratio [HR] 1.46; 95% CI 1.22-1.75; p < 0.001), reduced relapse incidence (HR 0.78; 95% CI 0.63-0.96; p = 0.020), and a trend toward inferior overall survival (OS, HR 1.13; 95% CI 0.98-1.30; p = 0.088). Moreover, patients who experienced both PES and acute GVHD had the highest 2-year NRM (31.7%; 95% CI 26.0%-37.6%) and the lowest 2-year OS (55.9%; 95% CI 50.0%-62.4%), compared with those who experienced either PES (NRM 20.7%; OS 65.0%) or acute GVHD (NRM 19.5%; OS 62.8%) (p < 0.001), highlighting the combined effects of these complications. This study, the largest to date on PES, demonstrates its clinical significance as an early complication with lasting effects on transplant outcomes.