102 EJ Lee, et al. • Outcome of HSCT for childhood ALL in second CR methodologies. Different modes of HLA typing posed a problem concerning patient classification according to HLA compatibility. A strict definition of “HLA-match” as an 8 of 8 allele complete match of high resolution-typed HLA, as is done currently in our institution, would classify many patients who underwent HSCT with a serologically matched donor, previous to implementation of high resolution typing, as having received “HLA-mismatched” transplanta- tions. In order to resolve this issue, all patients were categorized according to time-appropriate HLA methodology; that is, an “HLA- match” was defined as a complete match of HLA tested between donor and recipient at that point in time, be the method serologic or molecular. All but 2 patients received a total body irradiation (TBI)-based conditioning regimen, with TBI-cytarabine-cyclophosphamide±anti- thymocyte globulin (ATG) being the most commonly utilized regimen (n=31, 59%), followed by TBI-cyclophosphamide (n=15, 28%). Regimens without TBI included 1 busulfan-based and 1 carmustine- Table 3. Transplantation Characteristics (n=53) Characteristic Value Age at transplant (yr) 9.7 (0.9-20.7) Donor type Sibling 26 (49) Unrelated 27 (51) Cell source BM 42 (79) PBSC 11 (21) Donor age (yr) 20.5 (1-40) HLA compatibility* Match 38 (72) Mismatch 15 (28) Donor-recipient gender Female-male 13 (25) Others 40 (76) ABO compatibility Match 26 (49) Mismatch 27 (51) Conditioning regimen TBI-Ara-Cy±ATG 31 (59) Others 22 (42) GvHD prophylaxis CS+MTX 49 (92) Others 4 (8) Values are presented as median (range) or number (%). BM, bone marrow; PBSC, G-CSF-mobilized peripheral blood stem cells; HLA, human leukocyte antigen; TBI, total body irradiation; Ara, cytarabine; Cy, cyclophosphamide; ATG, anti-thymocyte globulin; GvHD, graft-versus- host disease; CS, cyclosporine; MTX, methotrexate. *HLA match includes either low or high resolution HLA match. based conditioning each. Graft-versus-host disease (GvHD) prophy- laxis consisted of cyclosporine and mini dose methotrexate (MTX) for 49 patients (92%), with the remaining patients receiving a com- bination of cyclosporine and mycophenolate mofetil±MTX. 2. Study endpoints Major study endpoints included engraftment, incidence of acute GvHD (grades II to IV) and chronic GvHD, disease-free survival (DFS) and overall survival (OS). Neutrophil engraftment was defined as the first of 3 consecutive days in which the absolute neutrophil count (ANC) was >1,000/mm3, and platelet engraftment was defined as the first of 3 consecutive days in which the platelet count was > 50,000/ mm3 with no platelet transfusions in the past seven days. Acute and chronic GvHD were classified according to previously established criteria11,12). DFS was defined as the time from HSCT till relapse or death, whichever came first. OS was defined as time from HSCT till death from any cause. Relapse rate and rate of 1-year transplant- related mortality (TRM) were also evaluated. 3. Statistical analyses Prognostic factors for DFS were evaluated using Cox proportional hazards regression model. The following variables were analyzed: age at initial diagnosis, age at transplant, patient gender, white blood cell (WBC) count at diagnosis, WBC count at relapse, initial risk group, duration of first CR, donor type, cell source, HLA compatibility, ABO compatibility, and conditioning regimen. Variables with aP value of <0.1 on univariate study were entered in a multivariate model using the backward stepwise selection method. Incidence of acute and chronic GvHD, relapse and TRM rates were calculated using a cumulative incidence function with consideration of competing risks. Variables studied for DFS were also evaluated for contributing to acute and chronic GvHD, relapse rate and TRM rate using Gray’s test. Again, factors with aP value of <0.1 were analyzed in a multivariate manner using Fine and Gray’s proportional hazards model. DFS and OS were calculated with the Kaplan-Meier method and comparisons done with the log rank test.P values<0.05 were considered statistically significant. Statistical work was done on SPSS ver. 12.0 (SPSS Inc., Chicago, IL, USA) and R package, ver. 2.10.1 (available from: http:// cran.r-project.org). Results 1. Engraftment data Median infused cell counts were as follows: TNC 2.6×108/kg (range, 0.7 to 42.1×108/kg), MNC 1.2×108/kg (range, 0.5 to 35.7× 108/kg), CD34+ 5.3×106/kg (range, 0.6 to 81.4×106/kg), CD3+