Korean J Pediatr 2012;55(3):100-106 • http://dx.doi.org/10.3345/kjp.2012.55.3.100 103 5.2×107/kg (range, 0.5 to 518×107/kg). All patients showed neu- trophil engraftment at a median of 15 days (range, 8 to 31 days), while only 38 patients (72%) showed full recovery of platelet count to greater than 50,000/mm3 at a median of 26 days (range, 10 to 178 days) post- transplantation. 2. Incidence of acute and chronic GvHD Acute GvHD of grade II or above was diagnosed in 24 patients at a median of 15 days post-transplantation (range, 5 to 81) for a cumulative incidence of 45.3±6.9%. Eighteen patients (34%) were diagnosed with grade II acute GvHD, and 3 patients each (6%) were diagnosed with grades III and IV GvHD. All 3 patients with grade IV GvHD died. Important risk factors for acute GvHD included age at transplant (P=0.090), donor type (P<0.001), and HLA compatibility (P =0.002), with only HLA compatibility having a significant effect on multivariate study (hazard ratio [HR], 2.41; 95% confidence in- terval [CI], 1.14 to 5.08;P =0.021). Chronic GvHD was diagnosed in 16 patients (mild 5, 9%; moderate 10, 19%; severe 1, 2%) for a cumulative incidence of 28.5±6.3%. Median time at chronic GvHD diagnosis was 5 months after trans- plantation (range, 2.7 to 17.2). No one factor had a significant impact on chronic GvHD incidence. 3. Analysis of DFS The estimated 5-year DFS for the entire cohort was 45.2±6.8%. On analyzing for prognostic factors for DFS, age at diagnosis (P = 0.071), donor type (P =0.010), and HLA compatibility (0.021) proved to be important variables (Table 4). However, on multivariate study, only donor type had prognostic significance (HR, 2.75; 95% CI, 1.28 to 5.93;P =0.010), with superior DFS in recipients from sibling donors compared to unrelated donors. Patients with a long duration of first CR before HSCT did not have a survival advantage compared with patients who relapsed early. DFS curves were redrawn in order to evaluate for potential comparable outcomes of MSD and MUD HSCT (Fig. 1). Five-year estimated DFS for MSD HSCT, MUD HSCT, and mismatched unrelated donor (MMUD) HSCT were as follows: 68±9.3%, 38.5± 13.5%, 14.3±9.4% respectively. Log-rank comparison of MSD and MUD HSCT showed a value bordering on statistically significant difference (P =0.051), while a comparison of MSD HSCT and MMUD HSCT showed clear differences in DFS (P =0.002). 4. Relapse and TRM incidence Overall, 15 patients relapsed resulting in an estimated 5-year rate of disease relapse of 28.9±6.4%. All patients showed bone marrow (BM) relapse except for 1 patient who was diagnosed with isolated testicular relapse 9 months post-transplantation. Analysis was done to determine factors significant for relapse using the variables utilized for study of DFS. Initial WBC count at diagnosis had prognostic relevance bordering on significance, with patients presenting with an Table 4. Univariate Study of Disease-free Survival Prognostic Factors Variable No. (Number) Events P value Age at diagnosis 0.071 ≥1 and <10 40 20 <1 or ≥10 13 10 Donor type 0.010 Sibling 26 10 Unrelated 27 20 HLA compatibility* 0.021 Match 38 17 Mismatch 15 13 Age at transplant 0.847 <10 27 15 ≥10 26 15 Gender 0.166 Male 42 26 Female 11 4 WBC count at diagnosis 0.563 <50,000 41 22 ≥50,000 12 8 WBC count at relapse† 0.707 <10,000 34 19 ≥10,000 16 10 Initial risk group 0.222 Low-standard 20 9 High-very high 33 21 Duration of first CR (mo) <12 / ≥12 and <36 11/18 7/13 0.524 <12 / ≥36 11/24 7/10 0.207 Cell source 0.478 BM 42 23 PBSC 11 7 ABO compatibility 0.837 Match 26 14 Mismatch 27 16 Conditioning regimen 0.884 TBI-Ara-Cy±ATG 31 19 Others 22 11 HLA, human leukocyte antigen; WBC, white blood cell; CR, complete remission; BM, bone marrow; PBSC, G-CSF-mobilized peripheral blood stem cells; TBI, total body irradiation; Ara, cytarabine; Cy, cyclophosphamide; ATG, anti-thymocyte globulin. *HLA match includes either low or high resolution HLA match. †WBC count at relapse was unavailable in 3 patients who were initially treated and showed first relapse at another institution, and who were subsequently transferred to our hospital for further treatment, including HSCT.