Evaluation of mixed hematopoietic chimerism in pediatric patients with leukemia after allogeneic stem cell transplantation by quantitative PCR analysis of variable number of tandem repeat and testis determination gene.

In order to monitor the clinical outcome of pediatric patients with leukemia following allogeneic hematopoietic transplantation, tests of variable number of tandem repeat (VNTR) and sex determination by quantitative polymerase chain reaction (PCR) were performed. PCR results combined with the blast counts from 21 leukemia patients were analyzed. Complete chimerism (100% donor cells) was found in 15 cases with remission, and incomplete chimerism in six cases with relapse. In the majority of cases, complete chimerism was always associated with no detectable blasts, while blasts were often detected in association with incomplete chimerism. There is significant correlation (P<0.0001) between the percentage of donor DNA and blast percentage in these patients. Early detection of incomplete chimerism may therefore predict a poor prognosis. In one patient (case 15), a differing percentage of donor DNA was observed between samples of bone marrow and peripheral blood collected on the same day. This may be due to the fact that allogeneic stem cells proliferate at different rates depending on their environment (bone marrow or peripheral blood). In addition, 100% donor cells found in the peripheral blood may not reflect the number of cells in the bone marrow. In case 17, asynchronous engraftment of donor cells was present between the white and red blood cell lineages, indicating that the degree of chimerism may not be the same in all cell lineages. At the time of this report, the significance of this observation is unknown and needs further investigation.

Developing a pediatric outpatient transplantation program. The Children's Memorial Hospital experience.

We describe the development of a pediatric outpatient transplant program and our initial experience with autologous and allogeneic transplants performed partially or completely in the outpatient setting. Forty-eight autologous and seven allogeneic transplants have been performed in our institution in the outpatient setting between June 1994 and July 2000. The ablation used for the autologous outpatient transplants was VP-16 1000 mg/m2/ day as a continuous infusion for 2 days and Carboplatinum 667mg/m2/day for 2 days. The autologous inpatient transplants received Thio-tepa 300-mg/ m2per day x 3 days and cyclophosphamide 60 mg/kg/day for 4 days. For those patients who received an immune-ablative allogeneic outpatient transplant, the regimen consisted of Fludarabine 30 mg/m2/day for 6 days, followed by busulfan for children less than five years of age 1 mg/kg/dose x 8 doses and for those five years and older 0.8 mg/kg/dose x 8 doses, followed by ATG 40mg/kg/day x 4 days. Engraftment was complete in all transplants achieving an ANC >500 for the outpatient transplant in 15 days (10-35) vs. the inpatient in 15 days (14-58). This was not statistically significant. They achieved un-sustained platelets >20.0 by day 19 (14-58) for the outpatients and day 32 10-64) for the inpatient. The allogeneic immune ablative transplants were considered engrafted when their VNTRs were greater that 30% which was achieved at a median of 13 days (10-27). The economic data showed a statistically significant decrease in charges and direct costs between the outpatient (median charges $30 775, direct costs $8 389) and the inpatient (median charges $99 838, direct costs $42 757) transplants (p0.001). There was no difference in morbidity and mortality between the two groups but the use of empiric amphotericin B was markedly decreased in the outpatient transplants. In conclusion it is feasible and less costly to perform autologous hematopoietic stem cell transplants in the outpatient setting with no increase in morbidity and mortality. For the allogeneic transplants there is not yet enough data to establish a similar conclusion.