Risk-Adjusted Outcome Measurement in Pediatric Allogeneic Stem Cell Transplantation

Impact of serum insulin-like growth factor-1 on HSCT outcome in pediatric cancer patients

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is associated with severe medical complications and variable outcome depending on the recipient's disease stage and health condition. Biomarkers predicting outcome may have therapeutic relevance in pediatric cancer care. Insulin like growth factor 1 (IGF 1) is a mitogenic and anabolic peptide hormone that is expressed in almost all tissues. This hormone is the major growth factor in childhood. As IGF 1 is decreased in conditions that cause catabolic metabolism, it may reflect the degree of physical robustness of the patient and serve as predictive biomarker for transplant outcome.

OBJECTIVES AND STUDY DESIGN

We evaluated the impact of pre-transplant serum-IGF 1 on both survival and adverse events in 587 pediatric cancer patients, who underwent autologous or allogeneic HSCT between 1987 and 2014 at the University Children's Hospital Tübingen, Germany. Survival probabilities of the entire cohort and of defined subgroups according to pre-transplant serum-IGF-1 were estimated using the Kaplan-Meier method.

RESULTS

Mean pre-transplant IGF 1 (n = 498) was low: -1.67 SDS (SD, 1.54). Completeness of follow-up three and ten years post HSCT was 96 % and 83 %, respectively. The ten-year overall survival was 44.8 % (95 % confidence interval [CI], 40.6-48.9). With decreasing IGF-1 SDS, there was a significant increase of transplant-related mortality (p = 0.027), sinusoidal obstruction syndrome (quartiles 4 to 1: 3; 1; 12; 12%; p < 0.001) and thrombotic microangiopathy (quartiles 4 to 1: 0: 0: 2; 5%; p = 0.004). IGF 1 decile 1 showed a significantly poorer outcome (p=0.042) with lower median (12 versus 68 months) and ten-year overall survival (37 % versus 52 %) when compared to decile 2-10.

CONCLUSIONS

This retrospective study suggests pre-transplant serum-IGF 1 as a predictor of survival and selected vascular adverse events that may have diagnostic and therapeutic relevance in pediatric cancer care.

Risk Factors for Transplant Outcomes in Children and Adolescents with Non-Malignant Diseases Following Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND The objective of this study was the analysis of transplant outcomes and survival in children treated with allogeneic hematopoietic cell transplantation (alloHCT) for non-malignant disorders, with a focus on risk factor analysis of transplant-related mortality (TRM). MATERIAL AND METHODS The treatment outcome was analyzed retrospectively in 10 consecutive years in 4 pediatric transplant centers in Poland. To compare the outcomes, patient data were analyzed according to the diagnosis, age at transplant, donor type, stem cell source, conditioning regimens, transplanted CD34+ cells dose, and pediatric TRM score. RESULTS From 183 analyzed patients, 27 (14.8%) died, all of them due to transplant-related complications. TRM occurred more frequently in matched unrelated donor (MUD) transplant recipients vs. matched sibling donor (MSD) transplant recipients (p=0.02); in peripheral blood (PB) recipients vs. bone marrow (BM) recipients (p=0.004); and in patients receiving >5×10⁶/kg CD34+ cells (p<0.0001). OS differed significantly according to underlying disease comparing to other diagnoses. Lower survival was found in patients transplanted from MUD (p=0.02). OS was higher in patients receiving BM (p=0.001) and in those receiving ≤5×10⁶/kg CD34+ cells (p<0.001). Multivariate analysis showed lower probability of TRM in BM recipients (p=0.04). The probability of TRM was higher in SCID patients (p=0.02) and in patients receiving >5×10⁶/kg CD34+ cells (p=0.0001). CONCLUSIONS Underlying disease, stem cell source, and CD34+ dose higher than 5×10⁶/kg were the most important risk factors for TRM, and they all affected OS.

Clearance of Hematologic Malignancies by Allogeneic Cytokine-Induced Killer Cell or Donor Lymphocyte Infusions

Well-established donor lymphocyte infusion (DLI) and novel cytokine-induced killer (CIK) cell therapy for the treatment of relapsing hematologic malignancies after allogeneic hematopoietic stem cell transplantation (HSCT) were compared with respect to feasibility, safety, and efficacy. Altogether, a total of 221 infusions were given to 91 patients (DLI, n = 55; CIK, n = 36). T cell recovery was significantly improved after CIK cell therapy (P < .0001). Although patients with CIK cell treatment showed a significantly worse prognosis at the time of HSCT (risk score, 1.7 versus 2.1; P < .0001), DLI and CIK cell therapy induced complete remission (CR) in 29% and 53% patients, respectively, whereas relapse occurred in 71% and 47%. In both groups, all patients with overt hematologic relapse at the time of immunotherapy (DLI, n = 11; CIK, n = 8) succumbed to their disease, while 36% and 68% patients with DLI or CIK cell therapy applied due to molecular relapse or active disease at the time of transplantation achieved CR. The 6-month overall survival rate in the latter patients was 57% and 77%, respectively, with a median follow-up of 27.9 months (range, .9 to 149.2 months). The 6-month cumulative incidence of relapse was 55% and 22% in patients who received DLI and CIK cell therapy, respectively (P = .012). Acute graft-versus-host disease developed in 35% of the patients who received DLI and in 25% of those who received CIK. No transfusion-related deaths occurred. These data, while underscoring the therapeutic value of conventional DLI, suggest the improved safety and to a certain extent efficacy of CIK cell therapy for patients at high risk for post-transplantation relapse of various hematologic malignancies.

Stem cell transplantation in sickle cell disease: therapeutic potential and challenges faced

INTRODUCTION

Sickle cell disease (SCD) is the most common inherited hemoglobinopathy worldwide, and is a life-limiting disease with limited therapeutic options to reduce disease severity. Despite being a monogenic disorder, the clinical phenotypes of SCD are variable, with few reliable predictors of disease severity easily identifying patients where the benefits of curative therapy outweigh the risks. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative option, though significant advances in gene therapy raise the promise for additional curative methods. Areas covered: Allogeneic transplantation in SCD has evolved and improved over the last two decades, now offering a standard of care curative option using a human leukocyte antigen (HLA)-matched sibling donor. Many of the seminal transplantation studies are reviewed here, demonstrating how initial failures and successes have influenced and led to current HSCT strategies. Such strategies aim to overcome setbacks and limitations, and focus on conditioning regimens, immune suppression methods, the use alternative donor sources, and gene therapy approaches. Expert commentary: SCD is a curable disease. Each dedicated effort to refine transplantation methods, expand the donor pool, and bring gene therapy models to fruition will make enormous impacts reducing disease burden and improving outcomes and quality of life for patients with SCD.

Transplant-related mortality and survival in children with malignancies treated with allogeneic hematopoietic stem cell transplantation. A multicenter analysis

The aim of the study was to assess the risk of TRM in pediatric patients treated for malignant disorders with allogeneic HSCT, according to different risk factors. The treatment outcome was analyzed in 299 pediatric patients treated in pediatric transplant departments from 2006 to 2015. To compare the outcome, patients were analyzed all together and in groups according to the diagnosis, age at transplant, donor type, disease status, stem cell source, and pediatric TRM score. At the end of the observation time, 82 patients were alive, 82 died, of which 40 due to transplant-related reasons. The most frequently observed causes of TRM were toxic complications effecting with organ failure (38%), followed by infections (26%), PTLD (14.3%), and GvHD (16.7%). There was no statistical difference in the incidence of TRM depending on stem cell source (P = .209) and primary diagnosis (P = .301). According to TRM score, TRM was significantly higher in high-risk group (P = .006). High-risk patients had lower survival comparing to low/intermediate group (P = .0001). OS did not differ between ALL, AML, and MDS/JMML groups. The study confirmed the utility of factors included in TRM score stratification in assessing the risk of transplant procedure in pediatric patients transplanted for malignancies.

Earlier Pediatric Psychology Consultation Predicts Lower Stem Cell Transplantation Hospital Costs

Objective

The purpose of this study was to examine the hypothesis that earlier time to psychology consultation would predict lower costs for the initial stem cell transplant (SCT) hospitalization among patients receiving care at a children's hospital.

Methods

A retrospective medical record review identified 75 patients (ages 0-32 years) with one or more visits by a licensed clinical psychologist during the initial SCT hospitalization from 2010 to 2014. Demographic and clinical variables were obtained from the electronic medical record and hospitalization costs were obtained from patient billing records. A generalized linear model with a gamma distribution and log link function was used to estimate the relationship between time to psychology consultation and cost for the initial SCT hospitalization while controlling for demographic, clinical, and utilization factors.

Results

After controlling for age at SCT, gender, race, insurance status, diagnosis, SCT type, length of stay, and number of psychology visits, earlier time to psychology consultation predicted lower costs for the initial SCT hospitalization (χ2 = 6.83, p = .01). When the effects of covariates were held constant, every day increase in the time to psychology consultation was associated with a 0.3% increase in SCT hospitalization costs (β = 0.003, SE = 0.001).

Conclusions

Results suggest that facilitating consultations with a pediatric psychologist early in the initial SCT hospitalization may reduce costs for patients undergoing SCT at children's hospitals. Future research is needed to determine the optimal timing of psychology consultation and quantify the economic impact of psychological services.

CD28 Blockade Ex Vivo Induces Alloantigen-Specific Immune Tolerance but Preserves T-Cell Pathogen Reactivity

Donor T-cells contribute to reconstitution of protective immunity after allogeneic hematopoietic stem cell transplantation (HSCT) but must acquire specific tolerance against recipient alloantigens to avoid life-threatening graft-versus-host disease (GvHD). Systemic immunosuppressive drugs may abrogate severe GvHD, but this also impedes memory responses to invading pathogens. Here, we tested whether ex vivo blockade of CD28 co-stimulation can enable selective T-cell tolerization to alloantigens by facilitating CD80/86-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) signaling. Treatment of human allogeneic dendritic cell/T-cell co-cultures with a human CD28 blocking antibody fragment (α-huCD28) significantly abrogated subsequent allospecific immune responses, seen by decreased T-cell proliferation and of type 1 cytokine (IFN-γ and IL-2) expression. Allo-tolerization persisted after discontinuation of CD28 blockade and secondary alloantigen stimulation, as confirmed by enhanced CTLA-4 and PD-1 immune checkpoint signaling. However, T-cells retained reactivity to pathogens, supported by clonotyping of neo-primed and cross-reactive T-cells specific for Candida albicans or third-party antigens using deep sequencing analysis. In an MHC-mismatched murine model, we tolerized C57BL/6 T-cells by ex vivo exposure to a murine single chain Fv specific for CD28 (α-muCD28). Infusion of these cells, after α-muCD28 washout, into bone marrow-transplanted BALB/c mice caused allo-tolerance and did not induce GvHD-associated hepatic pathology. We conclude that selective CD28 blockade ex vivo can allow the generation of stably allo-tolerized T-cells that in turn do not induce graft-versus-host reactions while maintaining pathogen reactivity. Hence, CD28 co-stimulation blockade of donor T-cells may be a useful therapeutic approach to support the immune system after HSCT.

Cost-Effectiveness of Defibrotide in the Prophylaxis of Veno-Occlusive Disease after Pediatric Allogeneic Stem Cell Transplantation

Veno-occlusive disease (VOD) remains a serious complication after allogeneic hematopoietic stem cell transplantation (HSCT). Prophylactic use of defibrotide (DF) might further reduce VOD rates but has no impact on the incidence of severe VOD or VOD-associated mortality. We investigated the cost-effectiveness of prophylactic DF according to the British Committee for Standards in Haematology/British Society for Blood and Marrow Transplantation guidelines in 348 children who underwent transplantation between 2001 and 2014 in our hospital, 138 of whom were at risk for VOD. The VOD incidence was 7.4% for the total cohort. Patients at risk had a higher incidence of VOD compared with patients without risk factors (15.2% versus 2.4%, P < .0001). VOD occurred more often in patients after busulfan-based myeloablative conditioning than in patients after total body irradiation (11.2% versus 3.5%, P = .001). Donor types or the transplantation-related mortality (TRM) risk score did not correlate with VOD incidence. In 81% of patients who responded to therapeutic DF, VOD resolved completely. Overall VOD-associated mortality was .3% for the complete cohort, 3.7% for patients diagnosed with VOD, and 20% for patients with severe VOD. Neither the cumulative incidence of TRM (19% ± 8% versus 17% ± 2%, P = .706) nor the median length of hospitalization differed between patients with VOD and patients without. The median costs per HSCT in patients with VOD were about one-third higher than the overall median costs per transplantation at our institution. The calculated total costs of prophylactic DF treatment for 138 patients at risk was almost 6 times as high as the incremental costs for patients with VOD. We conclude that prophylactic DF for children at risk for VOD is not cost-effective with respect to TRM and length of hospital stay.

Hematopoietic stem cell transplantation in thalassemia major and sickle cell disease: indications and management recommendations from an international expert panel

Thalassemia major and sickle cell disease are the two most widely disseminated hereditary hemoglobinopathies in the world. The outlook for affected individuals has improved in recent years due to advances in medical management in the prevention and treatment of complications. However, hematopoietic stem cell transplantation is still the only available curative option. The use of hematopoietic stem cell transplantation has been increasing, and outcomes today have substantially improved compared with the past three decades. Current experience world-wide is that more than 90% of patients now survive hematopoietic stem cell transplantation and disease-free survival is around 80%. However, only a few controlled trials have been reported, and decisions on patient selection for hematopoietic stem cell transplantation and transplant management remain principally dependent on data from retrospective analyses and on the clinical experience of the transplant centers. This consensus document from the European Blood and Marrow Transplantation Inborn Error Working Party and the Paediatric Diseases Working Party aims to report new data and provide consensus-based recommendations on indications for hematopoietic stem cell transplantation and transplant management.

Outcome of invasive mechanical ventilation after pediatric allogeneic hematopoietic SCT: results from a prospective, multicenter registry

Exact data on prognosis of children receiving invasive mechanical ventilation (IMV) after allogeneic hematopoietic SCT (HSCT) is lacking. We therefore started a prospective registry in four European university HSCT centers (Leiden, Paris, Prague and Utrecht) and their pediatric intensive care units (PICUs). The registry started in January 2009. In January 2013, the four centers together had treated a total of 83 admissions with IMV. The case fatality rate in these patients was 52%. Mortality 6 months after PICU discharge was 45%. There were significant differences between centers in the proportion of children who received IMV after HSCT (6-23%, P<0.01), in severity of disease on admission to PICU (predicted mortality 14-37%, P<0.01), in applying noninvasive ventilation before IMV (3-75% of admissions, P<0.01) and in the use of renal replacement therapy (RRT) (8-58% of admissions, P<0.01). Severe impairment in oxygenation, use of RRT and CMV viremia were independent predictors of mortality. Our study shows that mortality in children receiving IMV after HSCT remains high, but has clearly improved compared with older studies. Patient selection and treatment in PICU differed significantly between centers, which underscores the need to standardize and optimize the PICU admission criteria, ventilatory strategies and therapies applied in PICU.

A pediatric prognostic score for patients undergoing allogeneic hematopoietic stem cell transplantation

PURPOSE

The purpose of this study was to find and evaluate risk factors influencing the outcome of allogeneic hematopoietic stem cell transplantation (HSCT) in children and to develop a score stratifying patients by their risk of mortality.

METHODS

We retrospectively analyzed the effects of patient and donor characteristics as well as laboratory data including liver, iron, and inflammation parameters on the overall survival of 131 children and young adults with malignant and non-malignant diseases undergoing allogeneic HSCT.

RESULTS

In univariate analysis, 5-yr overall survival decreased significantly in patients with high disease risk (38% vs. 74%, P < 0.001), peripheral blood as graft source (47% vs. 73% for bone marrow, P < 0.001), ferritin >1500 ng/mL (41% vs. 79%, P = 0.001), C-reactive protein >10 mg/L (55% vs. 69%, P = 0.019), lactate dehydrogenase >6 μm∙s (22% vs. 67%, P = 0.001), gamma-glutamyl transpeptidase >1 μm∙s (43% vs. 68%, P = 0.035), and cholinesterase <60 μm∙s (36% vs. 70%, P = 0.002). For HLA recipient-donor match, there was a 5-yr overall survival of 81% for matched related, 58% for matched unrelated, 56% for mismatched unrelated, and 50% for haploidentical related donors (P = 0.020). We subsequently developed a score of parameters significant in multivariate analysis, that is, disease risk (HR = 4.1, P = 0.027), ferritin (HR = 6.4, P = 0.002), and cholinesterase (HR = 5.3, P = 0.027). For this score, 5-yr overall survival was 92% for the low-risk group, 66% for the intermediate-risk group, and 17% for the high-risk group (P < 0.001).

CONCLUSIONS

Disease risk, ferritin, and cholinesterase are factors decisively influencing the prognosis after HSCT and should be evaluated in further trials.

Effect of weight on outcomes of children undergoing hematopoietic cell transplantation

Chemotherapy dosing in hematopoietic cell therapy (HCT) conditioning regimens is based on patient weight. We hypothesized that potential underdosing or overdosing of patients with significant deviation of weight from normal might alter HCT outcomes, such as early mortality, overall or organ-specific toxicity, and/or relapse. We therefore conducted a retrospective analysis of 400 children between the ages of 2 and 18 years who underwent HCT for malignant or nonmalignant disease at Boston Children's Hospital over a 10-year period. Using the Centers for Disease Control and Prevention standard weight classification schema, we found no evidence to suggest a difference in survival or in time to engraftment or in relapse in patients with malignant disease. In the subgroups of patients either receiving autologous HCT or with underlying malignancy, combined overweight and obese patients had a higher rate of any organ, but not organ-specific, Grade 3-5 toxicity compared with the normal weight group. The study was not powered to detect a difference between underweight and normal weight patients. These data suggest that multiple outcome measures over the first year after HCT are unaffected by weight.

Stem cell transplantation after reduced-intensity conditioning for sickle cell disease

Sickle cell disease (SCD) is still associated with substantial morbidity and reduced life expectancy. Disease-related mortality rises to 14% in adolescents and young adults. Overall and disease-free survival following haematopoietic stem cell transplantation (HSCT) is 90% and 95%, respectively. To reduce transplant-associated late effects, the feasibility of a highly immunosuppressive reduced-intensity conditioning (RIC) regimen was explored in children with SCD and a matched sibling donor. Eight patients (median age, 9 yr) and symptomatic SCD were included. The conditioning regimen consisted of fludarabine, melphalan and either thiotepa or total lymphoid irradiation plus antithymocyte globuline or alemtuzumab. The graft was bone marrow in seven and cord blood in one case. The conditioning regimen was well tolerated and no severe infectious complications occurred. All patients displayed mixed chimaerism on day +28. After a median follow-up of 4 yr, 3/8 patients have mixed leucocyte chimaerism and 8/8 patients have 100% donor erythropoiesis. HSCT from matched sibling donors following a RIC regimen was well tolerated and resulted in cure in all patients studied. If confirmed in larger patient cohorts, these observations will have important implications for the indications of HSCT in children with SCD.

Long-term follow-up of children conditioned with Treosulfan: German and Austrian experience

We report the long-term follow-up of children transplanted with Treosulfan (TREO)-based conditioning in Germany and Austria. Nine centres reported a total of 109 transplantations. Patients were stratified according to the paediatric TRM risk score derived from the paediatric BMT registry (PRST) and compared with the historical transplant population of this registry. Underlying diseases were malignancies, immunodeficiencies, and haematologic and metabolic disorders. TREO total dose ranged from 21-42 g/m(2). Additional conditioning drugs included fludarabine, thiotepa, melphalan, CY and/or TBI. EFS at 3 years for non-malignant and malignant diseases was 88% and 49%, respectively. Leukaemia patients in remission had a survival of 51% at 3 years; nonremission patients relapsed and died within 18 months. TRM and OS in the low-risk groups 0 and 1 were similar to PRST controls. TRM in the high-risk groups 2 and 3 was markedly lower (9% vs 28% and 13% vs 53%, respectively) than in the PRST group, but OS was similar. In conclusion, TREO-based conditioning regimens in children resulted in excellent engraftment and long-term survival in nonmalignant disease. In high-risk malignancy, low acute toxicity was followed by low TRM but it did not translate into increased survival.

Lethal pulmonary complications after pediatric allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) in children is accompanied by a transplant-related mortality of 10% to 30%, which is the result of lethal pulmonary complications (LPCs) in many cases.

METHODS

We retrospectively assessed prevalence and risk factors of LPC following 234 allogeneic HSCTs in 228 patients for malignant or nonmalignant diseases at a single institution.

RESULTS

Pulmonary complications (PCs) were observed following 81 of 234 transplants (35%). LPCs were observed in 4% of HSCT within 100 days and in 14% within 5 years after HSCT. Late PCs after day 100 were lethal in 56% (22/39) of the patients with PCs, who are 11% (22/202) of all evaluable patients still alive after day +100. Causes of LPC after day 100 were viral (10 cases), bacterial (1 case), fungal (5 cases) pulmonary infection, or noninfectious (6 cases) PCs. Abnormal pretransplant pulmonary function test was not associated with an increased risk of LPC. Children older than 10 years and those undergoing a second HSCT had an increased incidence of overall LPC. T-cell depletion and mismatched donor HSCT (P = 0.001), but not age, were associated with an increased risk of lethal viral pneumonia.

CONCLUSIONS

Transplant-related mortality up to 5 years after HSCT in children was associated with LPC in 14%. There were more late (>100 days) than early LPCs, predominantly due to infectious etiologies and affecting children >10 years of age.

Exhaled nitric oxide and pulmonary complications after paediatric stem cell transplantation

Pulmonary complications are major causes of morbidity and mortality after haematopoietic stem cell transplantation (HSCT). We hypothesise that elevated exhaled nitric oxide (FeNO) levels early after HSCT in children are predictive for pulmonary complications. The present prospective study included 30 children (age, 4-18 years) before HSCT. FeNO levels were evaluated 10 days before transplant, at day 0, day +28 and day +60 after HSCT. During the follow-up period until day +100, pulmonary complications and lung function were assessed. Before HSCT, the mean FeNO levels were comparable in children with or without post-transplant pulmonary complications. However, they differed at day 0 and day +28 with a mean of 7 (±1.95) and 13 (±3.44) ppb at day 0 and a mean of 13 (±3.44) and 14 (±3.57) ppb at day +28, respectively.

CONCLUSION

Children with pulmonary complications after day +28 have higher mean FeNO levels 28 days after HSCT than children without later pulmonary complications. Therefore, FeNO could be an important diagnostic tool for hyperinflammatory response in bronchial epithelium after paediatric HSCT.

Radioimmunotherapy-based conditioning for hematopoietic cell transplantation in children with malignant and nonmalignant diseases

Targeted irradiation of the bone marrow with radiolabeled monoclonal antibodies (radioimmunotherapy) represents a novel therapeutic approach with both myeloablative and antileukemic potential. In an open-label, single-center pilot study, 30 pediatric and adolescent patients undergoing hematopoietic cell transplantation for malignant (n = 16) and nonmalignant (n = 14) disorders received treatment with a ⁹⁰Y-labeled anti-CD66 monoclonal antibody. Patients with a high risk of relapse (n = 7) received additional treatment with standard conditioning based on either total body irradiation or busulfan to intensify the antileukemic effect. In patients with comorbidities (n = 23), radioimmunotherapy was combined with a reduced-intensity conditioning regimen to reduce systemic toxicity. Preferential irradiation of the bone marrow was achieved in all patients. Nonrelapse mortality was 4 (13%) of 30 patients. In patients with malignant diseases, the probabilities of overall and disease-free survival at 2 years were 0.69 (95% confidence interval 0.37-0.87) and 0.46 (95% confidence interval 0.19-0.70), respectively. In patients with nonmalignant diseases, the probability of both overall and disease-free survival at 2 years was 0.94 (95% confidence interval 0.63-0.99). This pilot study demonstrates that radioimmunotherapy is effective in achieving myeloablation with low additional toxicity when used in combination with standard or reduced-intensity conditioning in young patients.

Treatment of pediatric chronic myeloid leukemia in the year 2010: use of tyrosine kinase inhibitors and stem-cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-SCT) remains the only proven cure for chronic myeloid leukemia (CML), a rare malignancy in childhood. With the excellent results induced by the tyrosine kinase inhibitor (TKI) imatinib in adults in the last decade, the appropriate management of children with CML has also changed radically, and only a minority are now transplanted as a front-line treatment. Data on pediatric experiences with imatinib in CML from controlled trials remain very limited, but this review of available data describes the role of imatinib in children with CML, addressing: 1) the starting dose; 2) pharmacokinetics in childhood; 3) possible adverse effects, with a focus on the still-growing skeleton; 4) early monitoring of treatment efficacy in an attempt to avoid failure; 5) the timing of allo-SCT in children; and 6) treatment of CML relapse after allo-SCT. Because the characteristics of CML in children seem to overlap extensively with what is described in adult internal medicine, most answers and pediatric algorithms are adapted from the treatment of CML in adults. Today in 2010, allo-SCT in children should be postponed until CML becomes refractory to imatinib. The approach for young patients with suboptimal responses is unclear because data on the efficacy and safety of second-generation TKIs in childhood are almost entirely missing. Other than being included in a formal trial on second-generation TKIs, allo-SCT for patients failing imatinib remains the first choice.