Koh et al. Journal of Experimental & Clinical Cancer Research 2011, 30:36 http://www.jeccr.com/content/30/1/36 last follow-up. LFS was defined as time from the date of last transplantation to the date of disease relapse, death during remission or last follow-up. NRM was defined as a death not related to disease. Neutrophil recovery was defined as an absolute neutrophil count of at least 500 cells/mm3 for three consecutive time points. Platelet recovery was defined as a count of at least 20 000 platelets/mm3 without transfusion sup- port. Acute GVHD (aGVHD) was defined in accor- dance with standard criteria [12]. Chronic GVHD (cGVHD) was evaluated in patients surviving for more than 100 days after allo-HCT and was classified into limited or extensive type [13]. Statistical analysis If the disease for which the patient underwent trans- plantation was present at the time of death or found at autopsy, we defined disease relapse/progression as the primary cause of death. Unadjusted survival probabilities were estimated using the Kaplan and Meier method and compared using the log-rank tests. Cumulative incidence curves were used in a competing-risks model to calcu- late the probability of aGVHD, cGVHD and NRM [14]. For neutrophil and platelet recovery, death before neu- trophil or platelet recovery was the competing event; for GVHD, death without GVHD and relapse were the competing events; and, for NRM, relapse was the com- peting event. In order to examine the impact of cGVHD on survival, we performed a landmark analysis, which divided patients according to their prior history of cGVHD at 6 months post-transplant [15]. We excluded from landmark analysis patients who died or relapsed less than 6 months after transplant, and did not use the information on whether or not patients developed cGVHD 6 months after transplant. Multivariable analy- sis of prognostic factors for the primary outcome could not be conducted due to lack of statistical power. Instead, we performed a landmark analysis, which divided patients according to the significant pre-trans- plant factors and their prior history of cGVHD at 6 months post-transplant. All P values were 2-tailed and considered statistically significant if the values were less than 0.05. All statistical analyses were performed using the PASW Statistics17.0 (SPSS Inc, Chicago, IL, USA) and the statistical software environment R, version 2.9.1. Results The baseline characteristics of the patients are shown in Table 1. Page 3 of 7 Median (Range) 6 (0-18) 319 (23-3738) 26.0 (0.2-100) Table 1 Baseline characteristics of study participants Variable Male sex Diagnosis de novo AML ALL CML-AP MDS overt AML PCL Cytogenetics Intermediate Poor ECOG PS 0 1 2 3 Status at allo-HCT Primary refractory/Refractory relapse/Untreated MDS overt AML No. chemo regimens prior allo-HCT Time from diagnosis to allo-HCT (days) Marrow blasts at allo-HCT Conditioning regimen Intensified Standard Reduced-intensity Reduced-intensity + cytoreductive chemotherapy GVHD prophylaxis None Calcineurin inhibitor alone Calcineurin inhibitor + sMTX Calcineurin inhibitor + MMF Donor (HLA-A, B and DRB1 antigens) Matched related PB/BM Mismatched related PB/BM Matched unrelated BM Mismatched unrelated BM Umbilical cord blood n (%) 24 (57.1) 17 (40.5) 12 (28.6) 2 (4.8) 10 (23.8) 1 (2.4) 17 22 2 (4.8) 25 (59.5) 7 (16.7) 8 (19.0) 7/32/3 9 (21.4) 12 (28.6) 7 (16.7) 14 (33.3) 3 (7.1) 5 (11.9) 32 (76.2) 2 (4.8) 10/2 3/1 19 1 6 allo-HCT: allogeneic hematopoietic cell transplantation; HLA: human leukocyte antigen; sMTX: short-term methotrexate; MMF: mycophenolate motefil; BM: bone marrow; PB: peripheral blood. patients, a platelet count > 20 000/μl was not achieved. In the patients that achieved platelet counts of ≥ 20 000/ μl, the median time to platelet engraftment was 33 days (range, 13-99). The cumulative probabilities of neutrophil and platelet engraftment were 79% and 55%, respectively. Engraftment Neutrophil engraftment was achieved in 33 (79%) of 42 patients. The median time to neutrophil engraftment was 17 days (range, 9-32). In a total of four of 27 evaluable GVHD Twenty-four of 42 patients developed aGVHD (eight grade I, nine grade II, five grade III, two grade IV). Twelve of 24 evaluable patients developed cGVHD (one