The effect of GVHD on transplant outcomes after unrelated cord blood transplantation (UCBT) is not yet fully understood. Pediatric patients aged 0–15 years with acute leukemia or myelodysplastic syndrome who underwent their first UCBT (n = 740) were selected from the Japanese registry. Fifty percent of the patients received a UCB unit containing more than 5.0 × 10⁷/kg total nucleated cells. The occurrence of grade III–IV acute GVHD was associated with a higher risk of non-relapse mortality (NRM, hazard ratio [HR] 4.07, P < 0.001) compared with no acute GVHD. Grade I–II acute GVHD was not associated with NRM. The occurrence of grade I–II or grade III–IV acute GVHD was not associated with a relapse risk. These findings showed that grade I–II acute GVHD carried no survival benefit and grade III–IV acute GVHD had an adverse effect (HR 1.68, P = 0.007). The occurrence of limited chronic GVHD was associated with a low risk of overall mortality (HR 0.60, P = 0.045). Severe acute GVHD should be prevented because of its association with high overall mortality and NRM in pediatric single UCBT. Mild acute GVHD provides no overall benefit. Mild chronic GVHD may be beneficial for survival.

尚未完全了解GVHD对无关脐血移植（UCBT）后移植结局的影响。 从日本登记处中选出接受初次UCBT（n = 740）治疗的0-15岁急性白血病或骨髓增生异常综合症的儿科患者。50％的患者接受了UCB单位，该单位包含超过5.0×10 ⁷ / kg的总有核细胞。发生III–IV级急性GVHD与较高的非复发性死亡风险（NRM，危险比[HR] 4.07，P <0.001），而无急性GVHD。I–II级急性GVHD与NRM无关。I–II级或III–IV级急性GVHD的发生与复发风险无关。这些发现表明，I–II级急性GVHD没有生存益处，而III–IV级急性GVHD则有不良反应（HR 1.68，P  = 0.007）。有限的慢性GVHD的发生与总死亡率的低风险相关（HR 0.60，P  = 0.045）。应当预防严重的急性GVHD，因为它与小儿单UCBT的高总死亡率和NRM相关。轻度急性GVHD无法提供整体益处。轻度慢性GVHD可能对生存有利。