Kyung Duk Park

Relative tumor burden predicts metastasis‐free survival in pediatric osteosarcoma

To analyze the significance of relative tumor burden in pediatric osteosarcoma.

Highly Variable Pharmacokinetics of Once-Daily Intravenous Busulfan When Combined with Fludarabine in Pediatric Patients: Phase I Clinical Study for Determination of Optimal Once-Daily Busulfan Dose Using Pharmacokinetic Modeling

Busulfan has a narrow therapeutic range, and in children, pharmacokinetic variability has been found to be high even after the use of intravenous (i.v.) busulfan. Recently, a reduced toxicity myeloablative regimen showed promising results, but the data of busulfan pharmacokinetics in hematopoietic stem cell transplantation (HSCT) using a targeted busulfan/fludarabine regimen in children has not yet been reported. We performed therapeutic drug monitoring (TDM) after once-daily i.v. busulfan combined with fludarabine and analyzed the outcomes. Busulfan (i.v.) was administered once daily for 4 consecutive days. The daily target area under the curve (AUC) was 18,125-20,000 μg*h/L/day (4415-4872 μmol*min/L/day), which was reduced to 18,000-19,000 μg*h/L/day (4384-4628 μmol*min/L/day) after a high incidence of toxicity was observed. A total of 24 patients were enrolled. After infusion of busulfan on the first day, patients showed AUC that ranged from 12,079 to 31,660 μg*h/L (2942 to 7712 μmol*min/L) (median 16,824 μg*h/L, percent coefficient of variation (%CV) = 26.5%), with clearance of 1.74-6.94 mL/min/kg (median 4.03 mL/min/kg). We performed daily TDM in 20 patients, and during the daily TDM, the actual AUC ranged from 73% to 146% of the target AUC, showing high intraindividual variability. The %CV of busulfan clearance of each individual ranged from 7.7% to 38.7%. The total dose of busulfan administered for 4 days ranged from 287.3 mg/m(2) to 689.3 mg/m(2). Graft failure occurred in 3 patients with total AUC less than 74,000 μg*h/L (18,026 μmol*min/L), and 2 patients with relatively high total AUC experienced veno-occlusive disease. Busulfan pharmacokinetics showed high inter- and intraindividual variability in HSCT using a targeted busulfan/fludarabine regimen, which indicates the need for intensive monitoring and dose adjustment to improve the outcome of HSCT. Currently, we are performing a newly designed phase II study to decrease regimen-related toxicities and reduce graft failure by setting an optimal target AUC based on this study.

Effects of Different Sensitization Events on HLA Alloimmunization in Solid Organ Transplantation Patients

OBJECTIVE HLA alloimmunization is caused by various sensitization events, such as transfusion, pregnancy, or organ transplantation. However, the effects of a particular sensitization event on HLA alloimmunization have not been well studied in parallel using an identical test method. We evaluated how different sensitization events affect the panel-reactive antibody (PRA) status in solid organ transplantation candidates. METHODS PRA identification tests were performed on 674 patients (354 males and 320 females) using Luminex assay kits (LIFECODES, Gen-Probe, Stamford, CT, United States). PRA-positive rates (HLA-A, B, or DR antibodies of median fluorescence intensity [MFI] values of ≥1000) and antibody strengths in PRA-positive cases were analyzed according to the different sensitization events and gender. RESULTS PRA (class I and/or II)-positive rates were significantly higher in patients with transfusion (33.0%; P = .001), pregnancy (71.4%; P < .001), or transplantation events (76.9%; P < .001) than in controls without any identifiable sensitization events (5.6%). Transplantation had the strongest immunization effect, especially for class II HLA antigens. Female compared with male patients (60.3% vs 34.2%; P < .001) and retransplantation compared with first transplantation candidates of kidney transplantation (80.2% vs 41.1%; P < .001) showed a significantly higher PRA-positive rate. Retransplantation candidates (MFI 14,164) showed significantly stronger antibody strength than first transplantation candidates (MFI 5456) and those with single sensitization events of transfusion (MFI 4185) or pregnancy (MFI 5548; P < .001 for each). CONCLUSION Solid organ transplantation appears to have the strongest HLA alloimmunization effect followed by pregnancy and transfusion, especially for class II HLA antigens.

Tandem High-Dose Chemotherapy and Autologous Stem Cell Transplantation in Young Children with Atypical Teratoid/Rhabdoid Tumor of the Central Nervous System

The feasibility and effectiveness of tandem high-dose chemotherapy and autologous stem cell transplantation (HDCT/autoSCT) were evaluated in children younger than 3 yr of age with atypical teratoid/rhabdoid tumors (ATRT). Tandem HDCT/autoSCT was administered following six cycles of induction chemotherapy. Radiotherapy (RT) was administered if the tumor relapsed or progressed, otherwise, it was administered after 3 yr of age. Tumors relapsed or progressed during induction chemotherapy in 5 of 9 patients enrolled; 3 of these 5 received tandem HDCT/autoSCT as a salvage treatment. One patient died from sepsis during induction chemotherapy. The remaining 3 patients proceeded to tandem HDCT/autoSCT; however, 2 of these patients showed tumor relapse/progression after tandem HDCT/autoSCT. All 7 relapses/progressions occurred at primary sites even in patients with leptomeningeal seeding. Toxicities during tandem HDCT/autoSCT were manageable. A total of 5 patients were alive with a median follow-up of 20 (range 16-70) months from diagnosis. Four of 5 patients who received RT after relapse/progression are alive. The probability of overall survival at 3 yr from diagnosis was 53.3% ± 17.3%. Our tandem HDCT/autoSCT is feasible; however, early administration of RT prior to tandem HDCT/autoSCT should be considered to improve the outcome after tandem HDCT/autoSCT.

Pharmacogenetic analysis of pediatric patients with acute lymphoblastic leukemia: a possible association between survival rate and ITPA polymorphism.

Genetic polymorphisms are important factors in the effects and toxicity of chemotherapeutics. To analyze the pharmacogenetic and ethnic differences in chemotherapeutics, major genes implicated in the treatment of acute lymphoblastic leukemia (ALL) were analyzed. Eighteen loci of 16 genes in 100 patients with ALL were analyzed. The distribution of variant alleles were CYP3A4*1B (0%), CYP3A5*3 (0%), GSTM1 (21%), GSTP1 (21%), GSTT1 (16%), MDR1 exon 21 (77%), MDR1 exon 26 (61%), MTHFR 677 (63%), MTHFR 1298 (29%), NR3C1 1088 (0%), RFC1 80 (68%), TPMT combined genotype (7%), VDR intron 8 (11%), VDR FokI (83%), TYMS enhancer repeat (22%) and ITPA 94 (30%). The frequencies of single nucleotide polymorphisms (SNPs) of 10 loci were statistically different from those in Western Caucasians. Dose percents (actual/planned dose) or toxicity of mercaptopurine and methotrexate were not related to any SNPs. Event free survival (EFS) rate was lower in ITPA variants, and ITPA 94 AC/AA variant genotypes were the only independent risk factor for lower EFS in multivariate analysis, which was a different pharmacogenetic implication from Western studies. This study is the first pharmacogenetic study in Korean pediatric ALL. Our result suggests that there are other possible pharmacogenetic factors besides TPMT or ITPA polymorphisms which influence the metabolism of mercaptopurine in Asian populations.

Peri-engraftment syndrome in allogeneic hematopoietic SCT.

Engraftment syndrome (ES) and pre-engraftment syndrome (pre-ES) are both inflammatory conditions that occur after hematopoietic SCT (HSCT) and are characterized by non-infectious fever and skin rash. Although the pathogenesis is not fully understood, both syndromes are similar, and could be defined as a new clinical syndrome, named as peri-engraftment syndrome (peri-ES). We retrospectively analyzed the clinical records in 176 pediatric patients, following allogeneic HSCT. We utilized the definition of ES by Spitzer as the diagnostic criteria, excluding ‘within 96 h of engraftment’ criteria. Thirty cases developed peri-ES with a cumulative incidence of 17.0%. High cumulative incidence (50%) was seen in patients who underwent a double-unit cord blood transplantation (DUCBT; P<0.01). Clinical findings of peri-ES are similar, regardless of the onset day, and encephalopathy was the most severe complication. In the DUCBT cohort, the use of TBI and early complete chimerism (⩽day 21) were identified as risk factors that predispose the development of peri-ES. We determined that both, ES and pre-ES, might have similar causes, which could be included in peri-ES. Particularly, it occurred more in DUCBT patients, which means that not only neutrophil engraftment but also immune reactions within the two units might contribute to peri-ES.

Double umbilical cord blood transplantation for children and adolescents

Umbilical cord blood transplantation (UCBT) with two units has been conducted with promising results in adults to overcome the limitation of low cell numbers. In an attempt to improve the outcomes, double UCBT was performed in children and adolescents. Sixty-one patients, including 44 acute leukemia, and 17 other hematologic diseases, received double UCBT. Donor-type engraftment achieved in 82% of patients. Except one patient with persistent mixed chimerism of two units, other 49 patients showed dominancy of one unit and only the CFU-GM was significant factor influencing dominancy. The event-free survival (EFS) of leukemia and other hematologic disease were 59% and 53%, respectively, and the EFS of acute leukemia patients who received transplant in first or second CR (68.6%) was significantly better than in those with advanced disease (22.2%) (P = 0.007). Among the factors influencing outcomes, low cell dose difference between two units (TNC difference/TNC of large unit <15%) were associated with higher TRM, relapse, and lower EFS. Double UCBT was a promising modality of transplant in children and adolescence. However, engraftment and other results were not so satisfactory yet. To improve the outcomes, development of new selection guideline, probably including cell dose difference between two units and technology to enhance engraftment and reduce transplantation-related mortality are warranted.

Respiratory Viral Infections after Hematopoietic Stem Cell Transplantation in Children

This study was performed to characterize respiratory viral infections in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT). Study samples included 402 respiratory specimens obtained from 358 clinical episodes that occurred in the 116 children of the 175 consecutive HSCT cohort at Seoul National University Childrens Hospital, Korea from 2007 to 2010. Multiplex reverse-transcription polymerase chain reactions were performed for rhinovirus, respiratory syncytial virus (RSV), parainfluenza viruses (PIVs), adenovirus, human coronavirus (hCoV), influenza viruses and human metapneumovirus. Viruses were identified in 89 clinical episodes that occurred in 58 patients. Among the 89 clinical episodes, frequently detected viruses were rhinovirus in 25 (28.1%), RSV in 23 (25.8%), PIV-3 in 16 (18.0%), adenovirus in 12 (13.5%), and hCoV in 10 (11.2%). Lower respiratory tract infections were diagnosed in 34 (38.2%). Neutropenia was present in 24 (27.0%) episodes and lymphopenia was in 31 (34.8%) episodes. Sixty-three percent of the clinical episodes were hospital-acquired. Three patients died of respiratory failure caused by respiratory viral infections. Respiratory viral infections in pediatric patients who have undergone HSCT are common and are frequently acquired during hospitalization. Continuous monitoring is required to determine the role of respiratory viruses in immunocompromised children and the importance of preventive strategies.

Pre-Engraftment Syndrome after Unrelated Cord Blood Transplantation: A Predictor of Engraftment and Acute Graft-versus-Host Disease

Pre-engraftment syndrome (PES) is poorly characterized, and its clinical significance and the prognostic impact after unrelated cord blood transplantation (CBT) are unclear. To address these issues, we retrospectively analyzed the incidence, risk factors, and clinical outcomes of PES in unrelated CBT recipients. Data of 381 patients who received unrelated CBT from 18 medical centers in Korea were reviewed. PES was defined as unexplained fever >38.3°C not associated with infection, and/or unexplained skin rash with or without evidence of fluid retention before neutrophil recovery. PES developed in 102 patients (26.8%) at a median of 7 days after CBT. Of these patients, 74 patients (72.5%) received intravenous corticosteroid at a median dose of 1 mg/kg/day, and of these, 95% showed clinical improvement. Risk factors for developing PES included low risk disease, myeloablative conditioning, graft-versus-host disease (GVHD) prophylaxis without methotrexate or corticosteroid, and >5.43 x 10(7)/kg infused nucleated cells. Absence of PES was one of the risk factors for graft failure in multivariate analysis. The cumulative incidence of grade II to grade IV acute GVHD by 100 days after CBT was higher in patients with PES than in those without PES (56.0% versus 34.4%, P < .01). PES was not associated with chronic GVHD, treatment-related mortality, relapse, or overall survival. PES seems to be common after CBT and may be associated with enhanced engraftment without significant morbidity.

Successful Treatment of Primary Central Nervous System Lymphoma without Irradiation in Children: Single Center Experience

Primary CNS lymphoma (PCNSL) is a very uncommon disease in children, and usually treated by chemotherapy, combined with focal or craniospinal radiotherapy (RT). However, adverse effects of RT are a concern. We evaluated the outcomes of childhood PCNSL, treated with systemic and intrathecal chemotherapy, but without RT. For fifteen years, six patients among 175 of non-Hodgkin lymphoma were diagnosed as PCNSL in Seoul National University Childrens Hospital and we analyzed their medical records retrospectively. Their male:female ratio was 5:1, and median age was 10.1 yr. The primary sites were the sellar area in three patients, parietal area in one, cerebellum in one, and multiple areas in one. Their pathologic diagnoses were diffuse large B-cell lymphoma in three patients, Burkitt lymphoma in two, and undifferentiated B-cell lymphoma in one. Five were treated with the LMB96 treatment protocol, and one was treated with the CCG-106B protocol. None had RT as a first-line treatment. One patient had a local relapse and received RT and salvage chemotherapy, without success. No patient had treatment-related mortality. Their estimated 5-yr event-free and overall survival rates were both 83.3%. In conclusion, PCNSL is a rare disease in childhood, but successfully treated by chemotherapy without RT.