Analysis of engraftment kinetics in pediatric patients undergoing autologous PBPC transplantation

A Review of Infections After Hematopoietic Cell Transplantation Requiring PICU Care: Transplant Timeline Is Key

Despite major advances in antimicrobial prophylaxis and therapy, opportunistic infections remain a major cause of morbidity and mortality after pediatric hematopoietic cell transplant (HCT). Risk factors associated with the development of opportunistic infections include the patient's underlying disease, previous infection history, co-morbidities, source of the donor graft, preparative therapy prior to the graft infusion, immunosuppressive agents, early and late toxicities after transplant, and graft-vs.-host disease (GVHD). Additionally, the risk for and type of infection changes throughout the HCT course and is greatly influenced by the degree and duration of immunosuppression of the HCT recipient. Hematopoietic cell transplant recipients are at high risk for rapid clinical decompensation from infections. The pediatric intensivist must remain abreast of the status of the timeline from HCT to understand the risk for different infections. This review will serve to highlight the infection risks over the year-long course of the HCT process and to provide key clinical considerations for the pediatric intensivist by presenting a series of hypothetical HCT cases.

CD34+ immunoselection of autologous grafts for the treatment of high-risk neuroblastoma

BACKGROUND

Graft contamination has been blamed for causing relapse in children with high-risk neuroblastoma (HRNB) after autologous hematopoietic stem cell transplantation (HSCT).

PROCEDURE

We report the long-term results of hematopoietic reconstitution, post-transplant complications, and clinical outcome of 44 children with HRNB treated with busulfan/melphalan high-dose chemotherapy followed by transplantation of purged CD34+ immunoselected autologous peripheral HSCT. Minimal residual disease (MRD) of grafts was evaluated by anti-GD2 immunofluorescence or tyrosine hydroxylase reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Contaminating neuroblasts were found in 19/38 grafts (50%) before CD34+ positive selection, and none after (technique sensitivity of one cell in 10(5)). A median of 6.5 × 10(6) CD34+ cells/kg (range 0.8-23.7) were transplanted with only 2% of TRM. Neutrophils and platelet recovery occurred within a median of 12 days (range 9-47) and 44 days (range 12-259), respectively, without any secondary graft failure. Twenty-three percents of patients experienced a sepsis (10/44) and 14% a pyelonephritis (6/44). Recurrence of varicella zoster virus occurred in 21% of patients (9/44). Negative RT-PCR MRD within the leukapheresis product and cis-retinoic acid therapy were significantly and independently associated to a better survival (P < 0.05). Overall and event-free survivals at 5 years post-transplant were at 59.3% and 48.3% respectively.

CONCLUSIONS

Besides high rates of manageable infections due to late immune recovery, transplantation with CD34+ immunoselected grafts in HRNB children was feasible and did not affect long-term hematopoiesis.

Autologous peripheral blood stem cell collections in children weighing less than 10 Kg with solid tumors: Experience of a single center

There have only been a few reports and limited performance of peripheral blood stem cell (PBSC) collection in very small children weighing less than 10 kg. In this study, we intended to evaluate the safety and yield of PBSC collection, with the efficacy of PBSC transplantation (PBSCT) in the smallest children with solid tumors. From January 1998 to February 2004, 173 children underwent PBSC collection in Samsung Medical Center, Korea. Of these, 15 (8.7%) children weighed less than 10 kg and their clinical diagnoses were neuroblastoma (10 cases), rhabdoid tumor (2 cases), rhabdomyosarcoma (2 cases), and Wilms tumor (1 case). PBSCs were collected following chemotherapy plus G-CSF mobilization. The median age and weight at the time of apheresis were 15 months and 9 kg, respectively. The median number of PBSC collection procedures per case was 4 (range, 2-7). The median cell yield per apheresis product was 0.95 (range, 0.01-33.32) x 10(6)/kg CD34+ cells and 1.96 (range, 0.12-23.39) x 10(8)/kg mononuclear cells. No complications associated with citrate toxicity and other adverse effect were observed during the procedures. After high-dose chemotherapy, 14 patients were reinfused with PBSCs alone and all showed successful hematopoietic recovery. We concluded that PBSC collection would be a safe and practical procedure, even when done in the smallest children, provided that adequate intravascular fluid volume and circulating red cell mass were maintained. Also, the use of PBSCs to support high-dose chemotherapy was well tolerated and might enhance hematological recovery in the smallest children showing the excellent efficacy of PBSCT.

Large volume leukapheresis in small children: safety profile and variables affecting peripheral blood progenitor cell collection

Large volume leukapheresis (LVL) has been proposed as a simplified single-apheresis approach to collect the target number of CD34(+) cells. We retrospectively analyzed results of LVL in cytokine-mobilized patients weighing less than 20 kg to evaluate adverse events and variables affecting the yield. The only major adverse event recorded was transient and reversible systolic hypotension (three episodes). All the other adverse events were mild and did not require treatment. In multivariate analysis leukocyte count (P=0.001) and younger age (P=0.009) affected the CD34(+) cell number in the peripheral blood before apheresis. The number of CD34(+) cells before the apheresis was the only variable affecting CD34(+) cell yield in multivariate analysis (P=0.0001). In all, 77% of patients achieved the target CD34(+) cell dose of 2 x 10(6)/kg in their first apheresis. Recruitment was seen in 72% of the procedures, and this was related to the total blood volume processed (P=0.0005).

Rapid-sequence tandem transplant for children with high-risk neuroblastoma

BACKGROUND

The majority of patients with high risk neuroblastoma (NB) still relapse.

PROCEDURE

We designed a Phase II trial for children with advanced NB utilizing a program of induction chemotherapy followed by tandem high-dose chemoradiotherapy with stem cell rescue (HDC/SCR) in rapid sequence. Fifty-five patients were evaluable, ages 1-14 years, and 97 cycles of HDC/SCR have been completed to date. Pheresis was possible for every patient, despite their young age, with an average of 7.2 x 10(6) CD34+ cells/kg available to support each HDC/SCR cycle.

RESULTS

Engraftment was rapid, with median time to neutrophil engraftment of 11 days. Five patients who completed the first HDC course did not complete the second and there were four toxic deaths. With a median follow-up of 24 months from diagnosis, 38 of 55 patients (3-year EFS 59%) remain event-free. A subset of the patients received stem cells purged by CD34 selection. The engraftment and EFS of these patients are similar to the overall group.

CONCLUSION

This work demonstrates that a tandem transplant regimen for high-risk NB is a feasible treatment strategy in children and may improve disease-free survival.

Using peripheral blood progenitor cells (PBPC) for transplantation in pediatric patients: a state-of-the-art review

This paper presents a state-of-the-art review of using mobilized-peripheral blood progenitor cells (PBPC) for transplantation in children. Our own data and those from Medline searches and meeting reports, are analyzed and presented for the different sections that involve transplantation. Recommendations concerning the choice of mobilization regimens, venous access, priming of separator extracorporeal line, anticoagulation, and number of CD34+ cells to infuse for rapid engraftment are proposed. In the allogeneic setting, we analyze ethical and safety aspects of pediatric donor mobilization and collection. Data from the literature suggest that the use of cytokine-mobilized PBPC for allogeneic transplantation appears to be safe both for pediatric donors and patients leading a rapid hematopoietic engraftment with a similar incidence of acute graft-versus-host disease (GVHD). The high incidence of chronic GVHD and its management emerge as the most concerning aspect in allogeneic PBPC transplantation.

Use of concurrent G-CSF + GM-CSF vs G-CSF alone for mobilization of peripheral blood stem cells in children with malignant disease

There is limited experience in the mobilization of peripheral blood progenitor cells (PBPC) in children and the optimal method for PBPC mobilization is unknown. The present study was conducted to ascertain whether mobilization with G-CSF + GM-CSF (group I) provides some advantage over G-CSF alone (group II) in terms of collected CD34+ cells and hematopoietic recovery following myeloablative conditioning in children with malignancies. An economic analysis was also performed. Each group comprised 21 consecutive patients. The mean number of aphereses was 1.5+/-0.5 in group I and 1.2+/-0.46 in group II (NS). The mean number of CD34+ cells was 3.8 x 106+/-4.03/kg in group I and 4.2+/-5.4 in group II (NS). The mean number of total blood volumes (TBV) processed was 4.4+/-1.5 in group I and 4.3+/-1.5 in group II (NS). The mean duration of the procedure was 276+/-74.1 min in group I and 286.7+/-75.9 min in group II (NS), and the inlet flow was 45.1+/-12 ml/min in group I and 39.5+/-15.1 ml/min in group II (NS). No significant differences in the neutrophil and platelet engraftment probability were observed between the two groups. The mean overall cost of group II was not statistically significant from that of group I (US$ 9521+/-330 vs US$ 10201+/-1028, P = NS). The cost of mobilization was significantly higher in group I than in group II, conditioning regimen costs were similar in both groups and the costs related to the post-transplant period were similar in both groups. We conclude that PBPC mobilization with G-CSF + GM-CSF in children does not enhance hematological recovery in comparison with mobilization using G-CSF alone. However, the combination of G-CSF + GM-CSF does not significantly increase the overall cost of transplantation.

CFU-Mk content of immunoselected CD34+ peripheral blood progenitor cells, evaluated with an adapted serum-free methylcellulose assay, is predictive of platelet lineage reconstitution in children with solid tumors

Immunoselected CD34+ peripheral blood progenitor cell (PBPC) transplantation is now frequently used to support autologous hematopoiesis after myeloablative therapy, its feasability having been proved by several groups. However, we and others observed delayed platelet recovery. We hypothesized that immunoselection processing might induce selective loss of megakaryocyte progenitors, or a decrease in their proliferation. We used a colony-forming units megakaryocyte (CFU-Mk) assay to evaluate these consequences and predict platelet recovery in patients. In CD34+ PBPCs from 10 children with solid tumors, we observed no selective loss in CFU-Mk numbers during immunoselection processing and no impairment of clonogenicity. The CFU-Mk yield (59.2 +/- 11.3%) was at least similar to the CD34+ yield (44.2 +/- 3.8%). We assessed the predictive value of CFU-Mk numbers infused for recovery of platelet lineage. We found an inverse correlation between the time taken to reach a platelet count greater than 50 x 10(9)/L and only the CFU-Mk dose (r = -0.71; p = 0.022) among the different type of progenitors, including colony-forming units granulocyte-macrophage (CFU-GM), burst-forming units erythrocyte (BFU-E) and colony-forming units-mixed (CFU-Mix). These findings suggest that CFU-Mk number could be used as sole predictive functional parameter for platelet reconstitution in children after immunoselection of CD34+ cells, in particular for low CD34+ cell dose, and thus as an indicator for initial quality of hematopoietic cells before in vitro expansion.

Tandem high-dose therapy in rapid sequence for children with high-risk neuroblastoma

PURPOSE

Advances in chemotherapy and supportive care have slowly improved survival rates for patients with high-risk neuroblastoma. The focus of many of these chemotherapeutic advances has been dose intensification. In this phase II trial involving children with advanced neuroblastoma, we used a program of induction chemotherapy followed by tandem high-dose, myeloablative treatments (high-dose therapy) with stem-cell rescue (HDT/SCR) in rapid sequence.

PATIENTS AND METHODS

Patients underwent induction chemotherapy during which peripheral-blood stem and progenitor cells were collected and local control measures undertaken. Patients then received tandem courses of HDT/SCR, 4 to 6 weeks apart. Thirty-nine patients (age 1 to 12 years) were assessable, and 70 cycles of HDT/SCR were completed.

RESULTS

Pheresis was possible in the case of all patients, despite their young ages, with an average of 7.2 x 10(6) CD34(+) cells/kg available to support each cycle. Engraftment was rapid; median time to neutrophil engraftment was 11 days. Four patients who completed the first HDT course did not complete the second, and there were three deaths due to toxicity. With a median follow-up of 22 months (from diagnosis), 26 of 39 patients remained event-free. The 3-year event-free survival rate for these patients was 58%.

CONCLUSION

A tandem HDT/SCR regimen for high-risk neuroblastoma is a feasible treatment strategy for children and may improve disease-free survival.

Oncology practice patterns in the use of hematopoietic growth factors

Recombinant hematopoietic growth factors were introduced into clinical practice a decade ago: erythropoietin in 1989, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in 1991, and interleukin-11 in 1997. The role of these agents in supportive therapy for children with cancer is still under considerable evaluation. This pediatric-based review summarizes current clinical applications, practice guidelines, and practice patterns for hematopoietic growth factors in the supportive care of children with cancer. It also discusses ongoing controversies and unanswered questions.