Nimotuzumab and radiotherapy for treatment of newly diagnosed diffuse intrinsic pontine glioma (DIPG): a phase III clinical study.

BACKGROUND: Diffuse intrinsic pontine glioma (DIPG) is a devastating cancer of childhood and adolescence. METHODS: The study included patients between 3 and 20 years with clinically and radiologically confirmed DIPG. Primary endpoint was 6-month progression-free survival (PFS) following administration of nimotuzumab in combination with external beam radiotherapy (RT). Nimotuzumab was administered intravenously at 150 mg/m2 weekly for 12 weeks. Radiotherapy at total dose of 54 Gy was delivered between week 3 and week 9. Response was evaluated based on clinical features and MRI findings according to RECIST criteria at week 12. Thereafter, patients continued to receive nimotuzumab every alternate week until disease progression/unmanageable toxicity. Adverse events (AE) were evaluated according to Common Terminology Criteria for Adverse Events (CTC-AE) Version 3.0 (CTC-AE3). RESULTS: All 42 patients received at least one dose of nimotuzumab in outpatient settings. Two patients had partial response (4.8%), 27 had stable disease (64.3%), 10 had progressive disease (23.8%) and 3 patients (7.1%) could not be evaluated. The objective response rate (ORR) was 4.8%. Median PFS was 5.8 months and median overall survival (OS) was 9.4 months. Most common drug-related AEs were alopecia (14.3%), vomiting, headache and radiation skin injury (7.1% each). Therapy-related serious adverse events (SAEs) were intra-tumoral bleeding and acute respiratory failure, which were difficult to distinguish from effects of tumor progression. CONCLUSIONS: Concomitant treatment with RT and nimotuzumab was feasible in an outpatient setting. The PFS and OS were comparable to results achieved with RT and intensive chemotherapy in hospitalized setting.

TGFß and IL10 have an impact on risk group and prognosis in childhood ALL.

BACKGROUND: Cytokines and their genes have been described to have an influence on incidence and prognosis in malignant, infectious and autoimmune disease. We previously described the impact of cytokine production on prognosis in paediatric standard-risk acute lymphoblastic leukaemia (ALL). PROCEDURE: In this study, we investigated the influence of cytokine gene polymorphisms (TNFα, TGFß, IL10 and IFNγ) on frequency, risk group and prognosis in 95 paediatric ALL-patients. We further report on intracellular production of these cytokines in T-cells. RESULTS: IL10 high-producer-haplotypes were reduced in ALL-patients compared with healthy controls and resulted in a reduced relapse rate compared with low-producer haplotypes. TGFß high-producer-haplotypes were correlated with a high initial blast-count (codon 25: G/G) and were elevated in high-risk ALL-patients (codon 10: T/T). IL10 was positively and IFNγ-production was negatively correlated with initial blast-count. At diagnosis the expression of TNFα and IFNγ was reduced in patients compared with healthy controls. This was more pronounced in high-risk and in T-ALL-patients. CONCLUSION: We conclude that gene-polymorphisms of the regulatory/anti-inflammatory cytokines, TGFß and IL10, but not of the pro-inflammatory cytokines, IFNγ and TNFα, have an impact on prognosis and risk-group of ALL. However, the reduced capacity to produce pro-inflammatory cytokines at diagnosis may serve as another important, functional risk factor. These data may help in further risk stratification and adaptation of therapy-intensity in paediatric patients with ALL.

Consensus of German transplant centers on hematopoietic stem cell transplantation in Fanconi anemia.

Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only curative therapy for the severe hematopoietic complications associated with Fanconi anemia (FA). In Germany, it is estimated that 10-15 transplants are performed annually for FA. However, because FA is a DNA repair disorder, standard conditioning regimens confer a high risk of excessive regimen-related toxicities and mortality, and reduced intensity regimens are linked with graft failure in some FA patients. Moreover, development of graft-versus-host disease is a major contributing factor for secondary solid tumors. The relative rarity of the disorder limits HSCT experience at any single center. Consensus meetings were convened to develop a national approach for HSCT in FA. This manuscript outlines current experience and knowledge about HSCT in FA and, based on this analysis, general recommendations reached at these meetings.

Successful treatment of an infant with CDA type II by intrauterine transfusions and postnatal stem cell transplantation.

Congenital dyserythropoietic anemias are rare hematological disorders leading to ineffective erythropoiesis with chronic anemia, complicated by iron overload. Here we present a remarkable clinical course of an infant with CDA type II who first presented as a severe fetal hydrops, requiring serial intrauterine red cell transfusions. While postnatal transfusion dependency persisted, the patient was successfully transplanted with a myeloablative conditioning regimen and peripheral blood stem cells of a matched donor. We believe that allogeneic HSCT is a reasonable therapeutic approach for patients with very severe CDA, even if only a matched unrelated donor is available.

Children with relapsed or refractory nephroblastoma: favorable long-term survival after high-dose chemotherapy and autologous stem cell transplantation.

BACKGROUND: High-dose chemotherapy (HDC) with autologous stem-cell rescue (ASCR) is a treatment option for pediatric patients with relapsed nephroblastoma. We present long term results of 9 patients treated between 1993 and 2013 at our center. PROCEDURE: Reinduction therapy was carried out according to GPOH and SIOP recommendations. The conditioning regimen consisted of carboplatin (1 200 mg/m²), etoposide (800 mg/m² or 40 mg/kg) and melphalan (180 mg/m²). Purging of the grafts with immunomagnetic CD34 positive selection was performed in 5 patients. RESULTS: 8 of 9 Patients (90%) are alive without evidence of disease after a median follow-up of 8.5 years. Leukocyte engraftment occurred after a median of 10 days (range 8-12). Median numbers of 667/µl CD3+, 329/µl CD4+, 369/µl CD8+T cells and 949/µl B cells were reached after 180 days. No negative impact of CD34 selection was observed. No transplantation-related death occurred. Acute toxicity comprised mucositis III°-IV° in all and veno-occlusive disease in one patient. Long term effects probably related to treatment occurred in 3/7 evaluable patients and comprised hearing impairment, reduced renal phosphate reabsorption, mild creatinine elevation and hypothyroidism (n=1, each). CONCLUSION: Thus, in our experience HDC with ASCR is an effective treatment of recurrent or refractory nephroblastoma with acceptable side effects. However, a randomized trial proving its efficiency with a high level of evidence is needed.

Testicular sex cord stromal tumors: analysis of patients from the MAKEI study.

BACKGROUND: In children and adolescents, testicular sex cord stromal tumors (TSCSTs) are rare. There is only limited information available regarding their clinical presentation, biology, and prognosis. METHODS: Between 1993 and 2009, 42 patients were prospectively reported to the cooperative MAHO and MAKEI studies on childhood germ cell tumors. Based on standardized documentation, data on epidemiology, clinical presentation, diagnostic features, histopathological differentiation, therapy, and follow-up were evaluated. RESULTS: During the study period, a gradual increase of the documentation of these rare tumors was observed. Palpable, indolent testicular swelling was the most common clinical finding. In three patients, retention of the testis was observed. Two patients showed sexual precocity, and one patient showed a 45X/46XY mosaic. Juvenile granulosa cell tumors (n = 16) and Sertoli cell tumor (n = 15) were the leading histopathological subtypes. The first were commonly diagnosed during the first weeks of life (median age: 6(0-162) days, the latter during infancy (median 7(0-14) months, P < 0.05). Other histological diagnoses included Leydig cell and Large Cell Calcifying Sertoli cell tumors (both n = 3) and not-otherwise-specified TSCSTs (n = 5), which were diagnosed during childhood and adolescence. All tumors were limited to the testis; there were no metastases. Treatment was surgical, only. After a median follow-up of 3.8 years, no relapse was observed. CONCLUSIONS: Diagnosis and therapy of testicular tumors should be planned in accordance with the recommendations of the respective childhood germ cell tumor protocols. High inguinal orchiectomy is safe and constitutes definitive therapy. Diagnostic work-up and follow-up should also consider potentially associated tumor predisposition syndromes.

Human leukocyte antigen distribution in German Caucasians with advanced Ewing's sarcoma.

BACKGROUND: Risk stratification criteria for patients with Ewing's sarcoma family of tumors (ESFT) are still limited. We hypothesized divergent human leukocyte antigen (HLA) patterns in ESFT patients and compared HLA-A, -B and -DR phenotype frequencies of patients with advanced ESFT with those of healthy controls. PATIENTS: HLA types of all German Caucasian patients with advanced ESFT and available HLA-A, -B and -DR data registered in the European Group for Blood and Marrow Transplantation, Paediatric Registry for Stem Cell Transplantation and the MetaEICESS data bases (study group, n=30) were retrospectively compared with HLA types of healthy German stem cell donors (control group, n=8 862 for single HLA frequencies and n=8 839 for allele combinations). Study group patients had been immuno-typed due to eligibility for allogeneic stem cell transplantation for high risk of treatment failure, and thus constituted a selected subgroup of ESFT patients. RESULTS: After Bonferroni correction for multiple testing (PC), phenotype frequencies of HLA-A24 remained significantly higher in the study group compared to controls (PC<0.05). Furthermore, several HLA combinations were significantly more frequent in the study group compared to controls (all PC<0.05). CONCLUSION: We report an increased incidence of circumscribed HLA patterns in German Caucasians with advanced ESFT. The possible clinical significance of this observation has to be re-assessed in prospective trials comprising larger ESFT patient numbers of all risk groups.

Allogeneic hematopoietic stem cell transplantation in Glanzmann thrombasthenia complicated by platelet alloimmunization.

BACKGROUND: For Thrombasthenia Glanzmann (GT) patients presenting with a severe clinical phenotype due to complete lack of thrombocyte function or increased titres of anti-platelet antibodies hematopoietic stem cell transplantation (SCT) is the only curative therapy. CASE REPORT: We report the case of a 13-month-old boy, presenting with a severe course of GT, who was successfully treated with an HLA-identical sibling bone marrow transplant. SCT was complicated by anti-platelet alloimmunization after platelet transfusion successfully treated with high dosage immunoglobulins (2 g/kg) and partial plasma exchange. CONCLUSION: SCT may be a viable option for selected patients with GT. However, SCT in GT carries its own significant risks, resulting from the development of anti-platelet antibodies. A critical risk-benefit analysis is mandatory prior to SCT.

[Whole-body MR imaging in children with suspected osteonecrosis after intensive chemotherapy: preliminary results]. / Ganzkörper-MRT bei Kindern mit Verdacht auf Osteonekrose nach intensiver Chemotherapie: Erste Ergebnisse.

PURPOSE: Use of multidrug chemotherapy poses the risk of avascular osseous necroses in children. Depiction of the whole body, including clinically non-apparent sites is mandatory for starting early and proper treatment, including surgical approaches in lesions near the joints. We analyzed the value of whole-body MRI in the detection of osteonecrosis, (1) in relation to conventional X-ray imaging and clinical symptoms, (2) using different MRI sequences, (3) with follow-up examinations. MATERIALS AND METHODS: 5 patients suffering from an oncological disease, 13 to 16 years old (3 x ALL, 1 x medulloblastoma, 1 x CML), and recently developing bone pain were examined with X-ray imaging of the particular region and a whole-body MRI (T2w TIRM, T 1w TSE sequences, pre- and post-contrast GD-DTPA, including fat suppression techniques). Neck/thorax/abdomen/pelvis, and upper and lower extremities were acquired in the coronal plane, and the feet in sagittal orientation. 4 of 5 patients had at least one follow-up examination (in the mean after 10 +/- 4 months). RESULTS: None of the initial X-ray images revealed an abnormal finding. The whole-body MRI showed in 4 of 5 children bone marrow lesions compatible with osteonecrosis. The locations were around the knee joints (n = 3) and the tibiae/ankle joints (n = 4). In addition to the symptomatic sites, MRI revealed additional lesions at the following sites: humerus (n = 5), hip joints (n = 4), knee joints (n = 6), ankle joints (n = 4). The size varied from small focal lesions to lesions measuring 90 % of the whole transverse diameter of the bone. The lesions were able to be detected most easily with heavily T 2-weighted (TIRM) sequences, and the diagnosis was most easily established using the non-enhanced TSE T 1-weighted sequences. As a consequence of the results of the whole-body MRI, all patients with lesions compatible with osteonecrosis received symptomatic (n = 2) or specific (n = 2) therapy. In the follow-up examinations, a higher number of patients showed no changes in the lesions as to size and distribution. 2 patients showed partial resolution of the osteonecroses. CONCLUSION: Whole-body MR imaging allows early diagnosis of symptomatic as well as clinically non-apparent osteonecroses. It can be used in planning and monitoring surgical and pharmacological therapies.

Influence of age on the outcome of 500 autologous bone marrow transplant procedures for hematologic malignancies.

PURPOSE: To determine the effect of age on the outcome of autologous bone marrow transplantation (ABMT) and/or peripheral-blood progenitor-cell (PBPC) transplantation. PATIENTS AND METHODS: A retrospective analysis was performed on 500 consecutive patients who ranged in age from 1 to 65 years (median, 40) with non-Hodgkin's lymphoma (NHL), Hodgkin's disease (HD), multiple myeloma (MM), or acute nonlymphoblastic leukemia (AML) who underwent autologous hematopoietic-cell transplant procedures at Stanford University Medical Center. RESULTS: The actuarial 5-year event-free survival (EFS) rate was 44%, the relapse rate 47%, and the regimen-related mortality (RRM) rate 8.6%. Disease status at time of transplantation, categorized as either minimal or advanced disease, was the strongest predictive factor for EFS (relative risk (RR) for advanced-disease group, 1.8; P < .0003) and relapse rate (RR for advanced-disease group, 1.9; P < .0004). Patients with minimal or advanced disease had an EFS rate of 48% and 30% and relapse rates of 43% and 72%, respectively. The EFS rate of patients less than 50 years verus > or = 50 years of age was 46% versus 34% (P = .03). Cox regression analysis showed that age was predictive for EFS (RR for patients 50 to 65 years, 1.4; P = .03). The actuarial RRM rate for these age groups was 7.4% versus 12.7% (P = .07), respectively. Multivariate analysis demonstrated that age (odds ratio [OR] for patients 50 to 65 years, 1.9; P < .05) and period of transplantation (OR for most recent years [1991 to 1995], 0.6; P = .06) were the most predictive factors for RRM. CONCLUSION: Although age greater than 50 years is associated with an inferior outcome following autologous hematopoietic-cell transplantation, it does not appear to be warranted to limit this potentially curative procedure based solely on age. The upper age limit of high-dose therapy with autologous progenitor-cell and/ or bone marrow support remains to be defined.

Does thalidomide affect IL-2 response and production?

The exact mechanism of immunosuppression by thalidomide is poorly understood. A common denominator in the pathogenesis of graft-vs.-host disease, graft rejection, reactional lepromatous leprosy, and autoimmune disorders modulated by thalidomide is the activation of T lymphocytes culminating in the synthesis of interleukin-2 (IL-2), the expression of high-affinity IL-2 receptors, and the induction of proliferation. We investigated the effect of thalidomide on the production of IL-2 by the human leukemia cell line Jurkat through induction of IL-2 gene enhancer activity and through the presence of IL-2 in supernatants. beta-galactosidase activity, encoded by a reporter lac z construct and controlled by a transcription factor in thalidomide-treated PMA- and ionomycin-stimulated Jurkat cells, was similar (97 +/- 1.33%; p > 0.1) to non-thalidomide-treated controls at all drug concentrations tested. IL-2 enhancer-driven beta-galactose activity of thalidomide-treated and stimulated cells was also similar to that of untreated controls (p > 0.2). The IL-2 production of activated nontransfected Jurkat cells was gauged by using the IL-2-dependent cell line HT-2 as a readout and by ELISA. Jurkat cells were subcloned by limiting dilution. Bulk cultures and three subclones (J.5.2.5., J.5.2.9., and J.5.3.8.) were assayed at 6, 12, and 24 hours after PHA/PMA-induced stimulation. No inhibitory effect on the IL-2 production by thalidomide could be detected at any of the drug concentrations tested (5-30 micrograms/mL), whereas 10 to 100 ng/mL of cyclosporine inhibited the IL-2 production by 95 to 100%. In addition, we observed neither inhibition of IL-2-dependent proliferation of HT-2 nor inhibition of PHA-induced proliferation of peripheral mononuclear cells by thalidomide at all drug concentrations used (5-30 micrograms/mL). These results do not support the possibility of a modulatory effect on the immune response by thalidomide via IL-2 production and IL-2 response.

Studies on the mechanism and specificity of the effect of the synthetic random copolymer GLAT on graft-versus-host disease.

Graft-versus-host disease (GVHD), which occurs when donor T-cells recognize multiple minor host histocompatibility antigens as non-self, presents the major limitation to successful allogeneic bone-marrow transplantation. The synthetic random copolymer of the amino acids, L-Glu, L-Lys, L-Ala and L-Tyr, termed GLAT, with promiscuous binding to multiple MHC class II alleles, reduces the incidence, onset and severity of disease in the BIO.D2 --> BALB/c model of lethal GVHD. GLAT inhibited the proliferative response towards host of both spleen cells from mice with GVHD and also of the effector T cell line established from these mice. Administration of GLAT for a limited period after transplantation completely abolished the cytotoxic activity toward host cells exerted by spleen cells from mice with GVHD. Whereas spleen and bone marrow cells from control mice with GVHD secreted IL-2 and INF-gamma when cocultured with host cells, these inflammatory cytokines could not be detected in supernatants of cells from GLAT treated mice. Moreover spleens and bone marrow cells from GLAT treated mice secreted small but significant amounts of IL-4 and IL-6 when cocultured with GLAT, suggesting that GLAT not only inhibits pro-GVHD cytokines but also causes a beneficial effect by inducing secretion of Th2 type cytokines. GLAT binds strongly to MHC molecules of host as well as donor haplotype. D-GLAT, identical to GLAT but composed of D-amino acids is also effective in preventing GVHD. D-GLAT does not cross-react with L-GLAT, but still binds strongly to MHC-class II molecules. These findings indicate that MHC blocking is involved in the therapeutic effect of GLAT on GVHD. The cumulative data demonstrate that GLAT modulates the effector mechanisms involved in GVHD, and can be potentially used for the prevention of GVHD across minor histocompatibility barriers.

GVHD: overview on pathophysiology, incidence, clinical and biological features.

Acute and chronic graft-versus-host disease (GVHD) develop in a significant proportion of transplant recipients and still represent one of the major causes of morbidity and mortality after allogeneic BMT. Prevention of GVHD does not only attempt to reduce acute toxicity and morbidity of transplantation but also to ameliorate long term outcome. GVHD is a T-cell mediated disease affecting multiple target organ systems. Recent research has tremendously improved our understanding of the pathophysiology of the disease. These new data are reviewed with main emphasis on their impact for children. The most important task for the future will be to make these new strategies fruitful for clinical application.

Additional immunotherapy on the basis of increasing mixed hematopoietic chimerism after allogeneic BMT in children with acute leukemia: is there an option to prevent relapse?

The success of allogeneic BMT (allo-BMT) in children with acute leukemias is mainly affected by relapse. There is evidence that these patients have only a little or no benefit from additional immunotherapy if the treatment is started in frank hematological relapse. Recently we were able to demonstrate that pediatric patients with acute leukemias and increasing mixed chimerism (MC) post-transplant have a significantly enhanced risk of developing relapse. We asked whether there is a possibility of preventing relapse, eg by withdrawal of post-transplant immunosuppression or by administration of donor lymphocytes in an early phase of the development of relapse. We present the case reports of two children (MDS and AML) with rapidly increasing MC in whom withdrawal of post-transplant immunosuppression or donor lymphocyte infusion (DLI) did prevent relapse.

Mixed hematopoietic chimerism after allogeneic bone marrow transplantation: the impact of quantitative PCR analysis for prediction of relapse and graft rejection in children.

It still remains unclear whether patients with mixed hematopoietic chimerism (MC) after allogeneic bone marrow transplantation (allo-BMT) have an increased risk of developing relapse or graft failure. To address this question, we monitored the individual dynamics of chimerism after allo-BMT in pediatric patients within a prospective case control study. The individual ratio of donor to recipient peripheral white cells was determined by quantification of genomic variable number of tandem repeats (VNTRs) with a polymerase chain reaction (PCR) approach. Within the study period from 1 January 1994 until 1 July 1996 we investigated 50 sequences of 46 pediatric patients after allo-BMT (32 with malignant, 18 with nonmalignant diseases). We found complete chimerism (CC) in 34/50 cases, MC in 12/50 follow-ups and 4/50 patients revealed autologous recovery (AC). Eight of 12 patients with MC showed increasing autologous patterns and subsequently relapsed or rejected their graft, 3/12 decreasing amounts of recipient DNA and turned to CC upon further follow-up. One patient of 12 who had severe combined immunodeficiency (SCID), attained engraftment with a stable MC pattern. Three patients of 34 with CC relapsed lacking a transitional MC interval. However, the time span between last CC confirmation and relapse in each of these three patients was 6 months or longer. We suggest that these patients also developed a stage of transitional MC but that the critical timepoint of molecular confirmation by PCR was missed as time intervals in the individual follow-up of these three patients were too long (> or = 6 months). In summary, the results demonstrate that the individual risk of developing relapse or graft failure is significantly enhanced in the MC situation (P < 0.0005). Therefore the quantitative analysis of MC at short time intervals might be of great value to identify high risk patients which will have a significantly/enhanced risk for relapse or graft rejection.

A prospective comparison of immune reconstitution in pediatric recipients of positively selected CD34+ peripheral blood stem cells from unrelated donors vs recipients of unmanipulated bone marrow from related donors.

Positively selected CD34(+) hematopoietic stem cells from unrelated donors (UD-HSCT) have been successfully transplanted, but little is known about immune reconstitution in this setting. Here we report a prospective comparison of immune reconstitution in recipients of UD-HSCT and of unmanipulated bone marrow from matched sibling donors (MSD-BMT). T-cell reconstitution occurred more than 100 days later in the UD-HSCT than in the MSD-BMT group. The first T cells after UD-HSCT were almost exclusively CD45RO(+) HLA-DR(+), whereas early-emerging T cells after MSD-BMT more frequently expressed CD62L, CD28, and CD25. In both groups, numbers of CD45RA(+) naive T cells increased after 180 days. After UD-HSCT, the T-cell-receptor (TCR)-repertoire was severely skewed and showed significantly reduced diversity during the first year, but only minor abnormalities were seen after MSD-BMT. TCR-diversity increased simultaneously with the number of naive T cells. In both groups, we observed transient expansions of gammadelta T cells. B cells were reconstituted more rapidly in UD-HSCT than in MSD-BMT recipients, whereas the rapidity of NK-cell reconstitution was similar in the two groups. In summary, T-cell reconstitution was slower after UD-HSCT than after MSD-BMT because of the delayed recovery of early memory-type T cells with reduced TCR-diversity, whereas naive T-, NK-, and B cells were reconstituted similarly in the two groups.

Transplantation of highly purified peripheral-blood CD34+ progenitor cells from related and unrelated donors in children with nonmalignant diseases.

Transplantation of allogeneic stem cells is currently the only curative treatment for some nonmalignant pediatric diseases. We investigated whether transplantation of purified CD34(+) stem cells prevents acute and chronic GvHD and reduces transplant-related mortality. A total of 25 pediatric patients with nonmalignant diseases underwent allogeneic transplantation from 26 donors (matched related n=4, matched or partially matched unrelated n=14, mismatched related n=8). All grafts were purified peripheral-blood CD34(+) stem cells mobilized with G-CSF. Patients received a median of 12.9 x 10(6) CD34(+) progenitor cells with a median of 6.1 x 10(3) contaminating T-lymphocytes per kilogram of body weight. No post transplant immunosuppressive drugs were given for prophylaxis of GvHD. Engraftment was seen in 21 patients. Three patients engrafted after a second transplant and one patient failed to engraft. Two patients had autologous reconstitution 1.5 years post transplant and one of them was successfully retransplanted. No acute GvHD >grade II was seen, and only two patients developed limited, chronic GvHD. In all, 22 patients (88%) are alive with a median follow-up of 3.7 years. In total, 19 patients (76%) are free of disease or of progression. Transplantation of highly purified peripheral-blood CD34(+) stem cells is associated with low toxicity in patients with nonmalignant diseases.

Megadose transplantation of purified peripheral blood CD34(+) progenitor cells from HLA-mismatched parental donors in children.

We performed HLA-mismatched stem cell transplantation with megadoses of purified positively selected mobilized peripheral blood CD34(+) progenitor cells (PBPC) from related adult donors in 39 children lacking an otherwise suitable donor. The patients received a mean number of 20.7 +/- 9.8 x 10(6)/kg purified CD34(+) and a mean number of 15.5 +/- 20.4 x 10(3)/kg CD3(+) T lymphocytes. The first seven patients received short term (<4 weeks) GVHD prophylaxis with cyclosporin A, whereas in all the following 32 patients no GVHD prophylaxis was used. In 38 evaluable patients, five patients experienced primary acute GVHD grade I and one patient grade II. In 32 patients, no signs of primary GVHD were seen and GVHD only occurred after T cell add backs. T cell reconstitution was more rapid if the number of transplanted CD34(+) cells exceeded 20 x 10(6)/kg. Of the 39 patients, 15 are alive and well, 13 died due to relapse and 10 transplant-related deaths occurred. We conclude that the HLA barrier can be overcome by transplantation of megadoses of highly purified mismatched CD34(+) stem cells. GVHD can be prevented without pharmacological immunosuppression by the efficient T cell depletion associated with the CD34(+) positive selection procedure. This approach offers a promising therapeutic option for every child without an otherwise suitable donor.