Table 2 Univariable analysis of impact of pre-transplant variables on overall survival Variable Age at allo-HCT < 40 ≥ 40 Diagnosis MDS overt AML Others Cytogenetics intermediate poor Marrow blasts at allo-HCT ≤ 26 > 26 Donor source Umbilical cord blood Others Survival (% at 5 y) 28 6 0 25 35 5 33 5 0 22 22 42 0 7 Log rank P value 0.055 0.015 0.013 0.013 <0.001 0.087 Koh et al. Journal of Experimental & Clinical Cancer Research 2011, 30:36 http://www.jeccr.com/content/30/1/36 Page 4 of 7 limited, 11 extensive). At five years, the cumulative probabilities of aGVHD and cGVHD were 63% and 37%, respectively. NRM A total of eight patients were alive at the time of this analysis, seven in complete remission (CR). The most common cause of death was disease relapse/progression. Causes of death were disease relapse/progression (n = 27), GVHD (n = 2), sinusoidal obstruction syndrome (SOS) (n = 3), Epstein-Barr virus associated post-trans- plant lymphoproliferative disorder (n = 1), and adeno- virus infection (n = 1). Of six patients with CNS lesion, five died of disease relapse/progression (n = 3), GVHD (n = 1) and SOS (n = 1), and one was alive at last fol- low-up although another HCT was planned due to BM relapse post-transplant. At five years, the cumulative probability of NRM was 38%. Nine patients died before day 30, and 18 patients died within the first 100 days post-HCT. LFS and OS A total of 22 of 33 evaluable patients attained a CR after the allo-HCT. The median follow-up of survivors was 85 months (range, 24-126 months). The five-year Kaplan- Meier estimates of LFS and OS were 17% and 19%, respectively. Univariable analysis We analyzed the impact of pre- and post-transplant characteristics on OS after allo-HCT. The factors included age at transplant, sex, primary vs. secondary leukemia, cytogenetics at diagnosis, number of BM blasts, donor type, myeloablative vs. reduced-intensity conditioning, and presence or absence of acute and chronic GVHD. Results of univariable analysis for OS are summarized in Table 2. In the univariable analyses of the impact of pre-transplant variables on OS, poor- risk cytogenetics, number of BM blasts (>26%), MDS overt AML and CB as stem cell source were significantly associated with worse prognosis (p = .03, p = .01, p = .02 and p < .001, respectively). In addition, based on a landmark analysis at 6 months post-transplant, the five- year Kaplan-Meier estimates of OS in patients with and without prior history of cGVHD were 64% and 17% (p = .022) respectively (Figure 1). Bivariable analysis We performed the landmark analyses at 6 months post- transplant, which classified patients according to signifi- cant pre-transplant factors including poor-risk cytoge- netics, number of BM blasts, or secondary leukemia and their prior history of cGVHD at 6 months post-trans- plant. Results of bivariable analysis for OS are shown in Conditioning Intensified Standard Reduced-intensity Reduced-intensity + cytoreductive chemotherapy allo-HCT: allogeneic hematopoietic cell transplantation. Figure 2, Figure 3 and Figure 4. The groups of patients with intermediate cytogenetics, marrow blast ≤ 26% or primary leukemia, who developed cGVHD less than 6 months after transplant, showed significantly or border- line significantly higher survival rates than those in the other groups (p = .039, p = .147, and p = .060, respec- tively). The five-year Kaplan-Meier estimates of OS in the patients with intermediate cytogenetics, marrow blast ≤ 26% or primary leukemia in addition to prior history of cGVHD were 75%, 83%, and 64%, respectively. Discussion Our data showed that allo-HCT resulted in long-term disease remission and an eventual cure of active leuke- mia in a subset of de novo AML or ALL patients with marrow blast ≤ 26% and without poor-risk cytogenetics, possibly by graft-versus-leukemia (GVL) effects mediated through cGVHD. A retrospective study with a large cohort using data reported to the Center for International Blood and Mar- row Transplant Research demonstrated that pre-trans- plant variables delineated subgroups with different long-