High-risk Pediatric Solid Tumors Research Articles

Multicenter real-world experience of the clinical efficacy and tolerance of pazopanib in high-risk pediatric solid tumors (PazoPed)

Pazopanib, a receptor tyrosine kinase inhibitor, exhibits anti-tumor activity in adult bone and soft-tissue sarcomas (STS), but has not yet been approved for pediatric tumors. The primary objective was to evaluate pazopanib efficacy when used alone or in combination with topotecan. This real-world multicenter retrospective study included patients with solid tumors, aged 25 years or less at the time of initial diagnosis, treated with pazopanib outside of a clinical trial. Nineteen patients were eligible for efficacy analysis: 14 bone tumors and 5 STS. At pazopanib initiation, the median age was 16.9 years, 18 patients had metastatic disease with a median of 2 prior therapeutic lines. With 6.2 months of median follow-up, no objective response was observed, but 10 patients (52.6%) had stable disease at 8 weeks and the 6-month disease control rate was 26.3%. The median progression free (PFS) and overall survival (OS) were 3.0 months and 6.2 months, respectively. Multivariate analysis showed an inverse relationship between the number of prior treatment lines and PFS and OS (hazard ratio = 1.73 (p = 0.04) and 1.76 (p = 0.03), respectively). Our study showed a potential tumor control activity of pazopanib in pediatric bone and soft tissue sarcomas. Further studies are warranted to determine the optimal timing and condition for pazopanib introduction to maximize the effect.

The hepatocyte growth factor/mesenchymal epithelial transition factor axis in high-risk pediatric solid tumors and the anti-tumor activity of targeted therapeutic agents.

Clinical trials completed in the last two decades have contributed significantly to the improved overall survival of children with cancer. In spite of these advancements, disease relapse still remains a significant cause of death in this patient population. Often, increasing the intensity of current protocols is not feasible because of cumulative toxicity and development of drug resistance. Therefore, the identification and clinical validation of novel targets in high-risk and refractory childhood malignancies are essential to develop effective new generation treatment protocols. A number of recent studies have shown that the hepatocyte growth factor (HGF) and its receptor Mesenchymal epithelial transition factor (c-MET) influence the growth, survival, angiogenesis, and metastasis of cancer cells. Therefore, the c-MET receptor tyrosine kinase and HGF have been identified as potential targets for cancer therapeutics and recent years have seen a race to synthesize molecules to block their expression and function. In this review we aim to summarize the literature that explores the potential and biological rationale for targeting the HGF/c-MET pathway in common and high-risk pediatric solid tumors. We also discuss selected recent and ongoing clinical trials with these agents in relapsed pediatric tumors that may provide applicable future treatments for these patients.

Adoptive Cellular Therapy for Pediatric Solid Tumors: Beyond Chimeric Antigen Receptor-T Cell Therapy.

Children and adolescents with high-risk (metastatic and relapsed) solid tumors have poor outcomes despite intensive multimodal therapy, and there is a pressing need for novel therapeutic strategies. Adoptive cellular therapy (ACT) has demonstrated activity in multiple adult cancer types, and opportunity exists to expand the use of this therapy in children. Employment of immunotherapy in the pediatric population has realized only modest overall clinical trial results, with success thus far restricted mainly to antibody-based therapies and chimeric antigen receptor T-cell therapies for lymphoid malignancy. As we improve our understanding of the orchestrated cellular and molecular mechanisms involved in ACT, this will provide biologic insight and improved ACT strategies for pediatric malignancies. This review focuses on ACT strategies outside of chimeric antigen receptor T-cell therapy, including completed and ongoing clinical trials, and highlights promising preclinical data in tumor-infiltrating lymphocytes that enhance the clinical efficacy of ACT for high-risk pediatric solid tumors.

Hematopoietic, Immune Recovery and Outcomes after Autologous Stem Cell Transplantation Following Plerixafor Plus G-CSF Versus Chemotherapy and G-CSF Based Mobilization in Pediatric Patients

Background: High-dose chemotherapy (HDC) and autologous stem-cell transplantation (ASCT) has shown survival benefits for chemo-sensitive high risk pediatric solid tumors. Collection of sufficient hematopoietic stem cells is required for ASCT. Plerixafor, a CXCR4 receptor antagonist, has been used when granulocyte colony-stimulating factor (G-CSF) and chemotherapy based (conventional) mobilization may not enable us to collect enough cells, especially in recurred or heavily treated patients. The experiences of plerixafor in pediatric patients are lacking as compared with adults, and immune reconstitution and outcomes in pediatric patients after ASCT with plerixafor based mobilization have not been reported in the literature as far as we have known. Therefore, we aimed to compare engraftment, hematopoietic and immune recovery and transplantation outcomes after ASCT between plerixafor plus G-CSF based and conventional mobilization group in pediatric patients.Methods: Propensity score matching (PSM) by optimal method with 1:1 ratio was performed to determine the control group. Age, sex, diagnosis, transplantation year, conditioning regimen, and number of transplantation were used as matching variables. We evaluated available parameters such as the day of neutrophil and platelet engraftment, absolute neutrophil counts (ANCs), absolute lymphocyte counts (ALCs), platelet and hemoglobin counts and lymphocyte subsets (CD3, CD4, CD8 [T cell] counts). Mann-Whitney U test was used to compare between two groups.Results: There were a total of 233 (21 plerixafor plus G-CSF based and 212 conventional mobilization group) patients who underwent HDC and ASCT in Seoul National University Children's Hospital between 2009 and 2016. By creating matched samples using PSM, 42 (21 plerixafor plus G-CSF based and 21 conventional mobilization group) patients were analyzed. The diagnoses were osteosarcoma in 14, brain tumor in 10, lymphoma in 6, neuroblastoma in 5, Ewing sarcoma in 4 and retinoblastoma in 3 patients. We used plerixafor plus G-CSF in patients who previously failed peripheral blood stem cell mobilization by chemotherapy and G-CSF. Patients received G-CSF (10 μg/kg) for 4 days, without prior chemotherapy. Then plerixafor (240 ug/kg) and G-CSF (10 ug/kg) were administered subcutaneously, at 10 and 2 hours before each apheresis. All 21 patients using plerixafor were mobilized successfully, and the median number of CD34+ cells were 10.65 (range 2.35-28.97) × 106/kg after 1 to 4 cycles of apheresis without serious complications. Fifty six ASCTs were performed, including 14 tandem transplantation. The median age at ASCT was 6 (range 3.7-22.4) years. All patients in conventional mobilization group achieved engraftment, but 2 patients in plerixafor plus G-CSF based mobilization group died due to acute respiratory distress syndrome before platelet engraftment and 1 patient died of sudden cardiac arrest before neutrophil and platelet engraftment. The engraftment tended to be faster in conventional mobilization group, but there was no statistically significant difference except for the day of ANC more than 0.5 × 109/L for 3 consecutive days (p=0.040). The ALC was lower in plerixafor plus G-CSF based mobilization group at one and six months after ASCT, respectively (p <0.001, p=0.041). The CD3, CD4 and CD8 count was lower in plerixafor plus G-CSF based mobilization group at one month after ASCT, respectively (p <0.001, p=0.007, p<0.001). The CD8 count was lower in plerixafor plus G-CSF based mobilization group (p=0.016), but the CD3 and CD4 count showed no statistical significant between-group differences at one year after ASCT, respectively (p=0.098, p=0.473). There was no significant between-group differences of overall survival (85.2% in plerixafor plus G-CSF based and 68.8% in conventional mobilization group, p=0.496) with a median follow-up duration of 22.7 (range 0.1-90.2) months.Conclusion: Hematopoietic and immune recovery tended to be slower in plerixafor plus G-CSF based mobilization group, but was done to a similar extent over time. In addition, transplant outcomes are similar between two groups. Our study suggests that plerixafor could be used safely and enabled more patients to procced to successful ASCT in pediatric patients. DisclosuresNo relevant conflicts of interest to declare.

Structural Optimization and Enhanced Prodrug-Mediated Delivery Overcomes Camptothecin Resistance in High-Risk Solid Tumors.

Camptothecins are potent topoisomerase I inhibitors used to treat high-risk pediatric solid tumors, but they often show poor efficacy due to intrinsic or acquired chemoresistance. Here, we developed a multivalent, polymer-based prodrug of a structurally optimized camptothecin (SN22) designed to overcome key chemoresistance mechanisms. The ability of SN22 vs. SN38 (the active form of irinotecan/CPT-11) to overcome efflux pump-driven drug resistance was tested. Tumor uptake and biodistribution of SN22 as a polymer-based prodrug (PEG-[SN22]4) compared with SN38 was determined. The therapeutic efficacy of PEG-[SN22]4 to CPT-11 was compared in: (i) spontaneous neuroblastomas (NB) in transgenic TH-MYCN mice; (ii) orthotopic xenografts of a drug-resistant NB line SK-N-BE(2)C (mutated TP53); (iii) flank xenografts of a drug-resistant NB-PDX; and (iv) xenografts of Ewing sarcoma and rhabdomyosarcoma. Unlike SN38, SN22 inhibited NB cell growth regardless of ABCG2 expression levels. SN22 prodrug delivery resulted in sustained intratumoral drug concentrations, dramatically higher than those of SN38 at all time points. CPT-11/SN38 treatment had only marginal effects on tumors in transgenic mice, but PEG-[SN22]4 treatment caused complete tumor regression lasting over 6 months (tumor free at necropsy). PEG-[SN22]4 also markedly extended survival of mice with drug-resistant, orthotopic NB and it caused long-term (6+ months) remissions in 80% to 100% of NB and sarcoma xenografts. SN22 administered as a multivalent polymeric prodrug resulted in increased and protracted tumor drug exposure compared with CPT-11, leading to long-term "cures" in NB models of intrinsic or acquired drug resistance, and models of high-risk sarcomas, warranting its further development for clinical trials. SIGNIFICANCE: SN22 is an effective and curative multivalent macromolecular agent in multiple solid tumor mouse models, overcoming common mechanisms of drug resistance with the potential to elicit fewer toxicities than most cancer therapeutics.

Enhanced Intratumoral Delivery of SN38 as a Tocopherol Oxyacetate Prodrug Using Nanoparticles in a Neuroblastoma Xenograft Model.

Purpose: Currently, <50% of high-risk pediatric solid tumors like neuroblastoma can be cured, and many survivors experience serious or life-threatening toxicities, so more effective, less toxic therapy is needed. One approach is to target drugs to tumors using nanoparticles, which take advantage of the enhanced permeability of tumor vasculature.Experimental Design: SN38, the active metabolite of irinotecan (CPT-11), is a potent therapeutic agent that is readily encapsulated in polymeric nanoparticles. Tocopherol oxyacetate (TOA) is a hydrophobic mitocan that was linked to SN38 to significantly increase hydrophobicity and enhance nanoparticle retention. We treated neuroblastomas with SN38-TOA nanoparticles and compared the efficacy with the parent prodrug CPT-11 using a mouse xenograft model.Results: Nanoparticle treatment induced prolonged event-free survival (EFS) in most mice, compared with CPT-11. This was shown for both SH-SY5Y and IMR-32 neuroblastoma xenografts. Enhanced efficacy was likely due to increased and sustained drug levels of SN38 in the tumor compared with conventional CPT-11 delivery. Interestingly, when recurrent CPT-11-treated tumors were re-treated with SN38-TOA nanoparticles, the tumors transformed from undifferentiated neuroblastomas to maturing ganglioneuroblastomas. Furthermore, these tumors were infiltrated with Schwann cells of mouse origin, which may have contributed to the differentiated histology.Conclusions: Nanoparticle delivery of SN38-TOA produced increased drug delivery and prolonged EFS compared to conventional delivery of CPT-11. Also, lower total dose and drug entrapment in nanoparticles during circulation should decrease toxicity. We propose that nanoparticle-based delivery of a rationally designed prodrug is an attractive approach to enhance chemotherapeutic efficacy in pediatric and adult tumors. Clin Cancer Res; 24(11); 2585-93. ©2018 AACR.

Abstract SY42-01: Emerging epigenetic targets in high-risk pediatric solid tumors

Abstract Pediatric cancers are typically characterized by simple genomes and key initiating events driven by aberrancy of a transcription factor or chromatin modifier. One such example is the most common extracranial solid tumor in children, neuroblastoma. Amplification of the transcription factor encoding gene MYCN is present in ∼50% of high-risk neuroblastomas, representing the best-characterized genetic marker of poor survival in these pediatric patients. We have focused on the discovery of new therapeutic strategies to targeting this recalcitrant subtype of neuroblastoma using chemical and functional genomic approaches. First, we identified BET bromodomain inhibitors as highly active in MYCN-amplified neuroblastoma in an unbiased screen of 673 diverse cancer cell lines and validated this finding using genetic suppression with shRNA and chemical inhibition with multiple BET inhibitors. Mechanistically, BET inhibitors suppress the MYCN transcriptional program and the expression of MYCN itself. Extending these studies in vivo, both to patient derived xenografts (PDX) and to genetically engineered mouse (GEM) models of MYCN-driven neuroblastoma, we demonstrated remarkable efficacy. However, this single agent approach was not curative, suggesting the need for combination therapies. In order to address this issue, we performed both gain-of-function (ORF) and loss-of-function (CRISPR/Cas9) screening of neuroblastoma cell lines treated with BET bromodomain inhibitors at an IC90 to identify potential mechanisms of resistance to treatment and to nominate targetable pathways for combination therapy. Three key pathways emerging at the intersection of these screens are under evaluation and will be presented. In parallel, we have performed a genome-wide CRISPR screen in a panel of 8 neuroblastoma cell lines, 7 of which are MYCN amplified, to identify new dependencies. In comparing neuroblastoma cell lines to over 70 non-neuroblastoma cancer cell lines, several known neuroblastoma dependencies were confirmed, including MYCN, ALK, and PHOX2B. Importantly, novel dependencies were revealed. Validated new dependencies will also be the topic of this presentation. Citation Format: Kimberly Stegmaier. Emerging epigenetic targets in high-risk pediatric solid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr SY42-01.

Targeting high-risk pediatric solid tumors with CAR T cells directed against ALK (anaplastic lymphoma kinase, CD246)

Neuroblastoma is the most common non-CNS tumor in children. Poor prognosis for patients presenting with high-risk disease underlines the need for novel therapeutic strategies. Chimeric antigen receptor T cell (CART) therapies combine the epitope specificity of a monoclonal antibody with the cytotoxicity of an activated T cell, and have demonstrated clinical efficacy in pediatric leukemia. To expand this approach to neuroblastoma, we focused on anaplastic lymphoma kinase (ALK), which can exist in native, over-expressed, or mutated forms and may help drive disease progression. Single chain variable fragments (scFvs) derived from four different monoclonal antibodies against ALK were used to construct second-generation CAR vectors featuring either CD28/CD3-zeta or CD137/CD3-zeta signaling domains. Some CAR constructs also included an IgG1 CH2CH3 spacer domain between the scFv and transmembrane domain. Retroviral vectors expressing ALK-specific CARs were generated and used to transduce human peripheral blood mononuclear cells. Transduction efficiencies ranged from 8% to 99%, depending on specific characteristics of each CAR construct. The resulting CART lysed ALK-positive neuroblastoma and Ewing's sarcoma cell lines and had minimal activity against an ALK-negative control. The ability to lyse tumor cells varied across scFvs, and short CART (no Ig spacer) showed enhanced lysis compared to long CARs (with Ig spacer). Short CART also produced Th1 cytokines (including IFN-gamma, IL-2, and TNF-alpha) when co-incubated with ALK-positive tumor lines; however, long CARs did not. Additionally, short anti-ALK CART significantly delayed the growth of human neuroblastoma in an NSG xenograft model when tumor-bearing mice were preconditioned with cyclophosphamide. Ongoing studies aim to: 1) further assess anti-ALK CART therapy in vivo in combination with modulation of suppressive murine myeloid populations; 2) explore mechanisms of ALK-positive neuroblastoma resistance to CART-mediated eradication; 3) characterize ALK protein expression in murine central nervous system tissues to better understand possibility of on-target, off-tumor toxicities with this therapy. Ultimately, anti-ALK CART could provide a novel therapy for pediatric solid tumors expressing cell-surface ALK.

Inhibition of STAT3 with orally active JAK inhibitor, AZD1480, decreases tumor growth in Neuroblastoma and Pediatric SarcomasIn vitroandIn vivo

The IL-6/JAK/STAT pathway is a key signal transduction pathway implicated in the pathogenesis of many human cancers, suggesting that kinase inhibitors targeting JAK/STAT3 may have a broad spectrum of antitumor activity. AZD1480, a pharmacological JAK1/2 inhibitor, exhibits anti-tumor potency in multiple adult malignancies. To evaluate the efficacy of inhibition of JAK/STAT3 signal transduction pathway we assessed the activity of AZD1480 in pediatric malignancies using preclinical models of three highly malignant pediatric solid tumors: neuroblastoma (NB), rhabdomyosarcoma (RMS) and the Ewing Sarcoma Family Tumors (ESFT). In this study, we employed panels of biomedical and biological experiments to evaluate the in vitro and in vivo activity of AZD1480 in NB, RMS and ESFT. Our data indicate that AZD1480 blocks endogenous as well as IL-6 induced STAT3 activation. AZD1480 decreases cell viability in 7/7NB, 7/7RMS and 2/2 ESFT cell lines (median EC50 is 1.5 μM, ranging from 0.36-5.37 μM). AZD1480 induces cell growth inhibition and caspase-dependent apoptosis in vitro and decreases expression of STAT3 target genes, including cell cycle regulators CyclinD1, 3 and CDC25A, anti-apoptotic genes Bcl-2 and survivin, the metastasis-related factor TIMP-1 and c-Myc. In vivo studies showed AZD1480 significantly decreased tumor growth and prolonged overall survival in tumor-bearing mice. Tumors from AZD1480-treated mice showed inhibition of activated STAT3 as well as decreased expression of STAT3 downstream targets. Our study provides strong evidence of the anti-tumor growth potency of JAK inhibitor AZD1480 in pediatric solid tumors, providing proof-of principle that inhibition of the JAK/STAT3 signal transduction could be a promising therapeutic target for high-risk pediatric solid tumors.

Hematologic Recovery after Tandem High-Dose Chemotherapy and Autologous Stem Cell Transplantation in Children with High-Risk Solid Tumors

Although the number of studies using tandem high-dose chemotherapy and autologous stem cell transplantation (HDCT/autoSCT) for the treatment of high-risk pediatric solid tumors has been increasing, documentation of hematologic recovery after tandem HDCT/autoSCT is very limited. For this reason, we retrospectively analyzed the hematologic recovery of 236 children with high-risk solid tumors who underwent tandem HDCT/autoSCT. The median numbers of CD34+ cells transplanted during the first and second HDCT/autoSCT were 4.3 × 106/kg (range 0.6-220.2) and 4.1 × 106/kg (range 0.9-157.6), respectively (P = 0.664). While there was no difference in neutrophil recovery between the first and second HDCT/autoSCT, platelet and RBC recoveries were significantly delayed in the second HDCT/autoSCT (P < 0.001 and P < 0.001, respectively). Delayed recovery in the second HDCT/autoSCT was more prominent when the number of transplanted CD34+ cells was lower, especially if it was < 2 × 106/kg. A lower CD34+ cell count was also associated with increased RBC transfusion requirements and a higher serum ferritin level after tandem HDCT/autoSCT. More CD34+ cells need to be transplanted during the second HDCT/autoSCT in order to achieve the same hematologic recovery as the first HDCT/autoSCT.

Early Clinical Experience of aAPC Activated NK-DLI Following Allogeneic PBSCT in Pediatric Solid Tumor Patients.

AbstractAbstract 3013 Background:Allogeneic Hematopoietic Stem Cell Transplant (alloHSCT) is effective in some hematologic malignancies and studies of alloHSCT for ultra high-risk pediatric solid tumors have shown some promise. Preclinical data demonstrates that activated NK cells readily kill pediatric solid tumors and leukemias, large numbers of activated NK cells can be generated ex vivo using artificial APCs (aAPCs) and the post-transplant period may be favorable for expansion and survival of adoptively transferred NK cells. Methods:We initiated a Phase I trial to assess feasibility and toxicity of escalating doses of donor-derived activated NK cell donor lymphocyte infusions (NK-DLI) on days 7 and 35 days following HLA-matched T cell depleted PBSCT in children and young adults with ultra-high risk solid tumors and leukemias. Donors underwent a single apheresis for filgrastim mobilized PBSC. The product was T cell depleted and CD34 and CD56 selected prior to cryopreservation, and the CD56+ fraction was cultured for 9–11 days with a K562 based aAPC expressing 4-1BBL and IL-15Ra plus rhIL-15 to generate the NK-DLI. NK-DLI consistently expressed high levels of natural cytotoxicity receptors NKp44 and NKp46 and mediated potent cytotoxicity ex vivo. T cell addback to the CD34 selected graft was performed to administer a T cell dose of 0.8–1.4 × 10e4 T cells/kg. Except for two pilot patients where NK-DLI was infused following engraftment, NK-DLI were administered ∼Day 7 and 35 post-transplant. Patients received a reduced intensity preparative regimen (fludarabine 30 mg/m2 and cyclophosphamide, 1200 mg/m2 on days –6 to -3; and melphalan 100 mg/m2 on day -2), and no prophylactic immunosuppression. Results:Seven patients with sarcomas were transplanted with NK-DLI infusion (1×10e5 CD56+ cells/kg/dose). Engraftment was brisk (median platelet recovery at 8d and neutrophil recovery at 9d). Patients had full donor myeloid chimerism by day 14 and all but one had >80% lymphoid chimerism by day 28. Patient #1 received NK-DLI on day +24 following alloHSCT and experienced aGVHD within 24 hours of NK-DLI with bullous skin rash and voluminous diarrhea. Prior to infusion the patient had what appeared to be a viral rash and fevers (skin biopsy negative for GVHD), but in retrospect likely GVHD, which was exacerbated by NK-DLI. Patient #2 received NK-DLI on Day +15 with no adverse effects. Subsequent patients enrolled onto cohort 1 with planned NK-DLI at days 7 and 35 (+7). Two patients developed aGVHD (rash and diarrhea), one with a cytokine-type reaction (fevers, hypotension) within 48 hours of NK-DLI infusion and one with aGVHD starting 21 days post NK-DLI. All 3 patients with matched unrelated donors experienced aGVHD after NK-DLI, whereas the 5 patients with matched sibling donors had no apparent adverse reactions nor GVHD. Persistence/engraftment of infused NK-DLI cannot be definitively determined, however, mean NK cell counts measured pre-alloHSCT and day +28 are 165/mm3 and 668/mm3 in the present cohort (n=6) compared to 149/mm3 and 395/mm3 in a historical alloHSCT population that did not receive NK-DLI (n=24). Antitumor effects via PET imaging were observed in patients with measurable disease and those without disease at the time of transplant have remained NED. Conclusions:Ex-vivo, aAPC expanded NK-DLIs do not interfere with stem cell engraftment but may contribute to or induce aGVHD, particularly in patients with matched, unrelated donors. Preliminary results suggest that aAPC NK-DLI expand in vivo and mediate antitumor effects following allogeneic PBSCT.Table:PatientAge/GenderDiseaseNK Cell DoseDay of NK Infusion (post-HSCT)DonorLikely NK Related ToxicitiesAnti-tumor EffectsStatusPre-HSCT NK CountPost-HSCT/NK1 Count (day 28-35)134 y FDSRCT1 × 105/kgDay 24MUDGrade IV GVHDPET and CT responseDoD-day + 190861883233 y MEwing's1 × 105/kgDay 14MSDNonePET responseDoD-day + 17122257322 y MDSRCT1 × 105/kgDay 9MUDFever, Grade II GVHDCRNED298762416 y MEwing's1 × 105/kgDay 8, Day 33MUDFever, Grade III GVHDRemains NEDNED179180524 y MDSRCT1 × 105/kgDay 8, Day 35MSDNonePR/CRMRD/NED119428618 y MARMS1 × 105/kgDay 8, Day 36MSDNoneRemains NEDNED85698714 y MEwing's1 × 105/kgtoo earlyMSDtoo earlytoo earlyNEDMEAN165668 Disclosures:No relevant conflicts of interest to declare.

Mobilization and Harvesting of Peripheral Blood Stem Cells in Pediatric Patients With Solid Tumors

Survival of patients with high-risk pediatric solid tumors has improved with the introduction of a high-dose chemotherapy regimen and autologous stem cell rescue. Here, we present our data regarding the evaluation of the efficacy and safety of hematopoietic stem cell mobilization and harvesting in children with solid tumors. From November 2002 to March 2010, 85 children underwent autologous peripheral blood stem cell collection; 35 (41.1%) of them weighed less than 20 kg and were diagnosed with neuroblastoma, Wilms' tumor, medulloblastoma, yolk sac sarcoma, or non-Hodgkin's lymphoma. The mobilization regimens included disease-specific chemotherapy plus granulocyte colony-stimulating factor in most of the patients. The median age and weight at the time of apheresis was 36 months and 13.5 kg, respectively. Large-volume leukapheresis was performed with the aim of reducing the psychological and financial impact of leukapheresis by reducing the number of procedures while collecting a large number of cells. The median number of mobilization and leukapheresis procedures per case was one. The pre-apheresis CD34+ cell count ranged from 2 to 845 µL, with a median of 24 µL. A median of four patient blood volumes was processed per procedure, lasting 279 min (range, 113-420 min). A radial catheter was used for harvesting in 35 procedures (71.4%). The median yield of CD34+ cells was 6.6×10(6) /kg per patient. The targeted dose of 5×10(6) /kg CD34+ cells was realized in 80% of patients. The tolerance of peripheral blood stem cell collection in our patients was good. In conclusion, the collection of peripheral blood stem cells is an effective and safe procedure, even when conducted on the youngest children.

HLA-Mismatched Hematopoietic Stem Cell Tranplantation for Pediatric Solid Tumors

Even if the overall survival of children with cancer is significantly improved over these decades, the cure rate of high-risk pediatric solid tumors such as neuroblastoma, Ewing's sarcoma family tumors or rhabdomiosarcoma remain challenging. Autologous hematopoietic stem cell transplantation (HSCT) allows chemotherapy dose intensification beyond marrow tolerance and has become a fundamental tool in the multimodal therapeutical approach of these patients. Anyway this procedure does not allow to these children an event-free survival approaching more than 50% at 5 years. New concepts of allogeneic HSCT and in particular HLA-mismatched HSCT for high risk solid tumors do not rely on escalation of chemotherapy intensity and tumor load reduction but rather on a graft-versus-tumor effect. We here report an experimental study design of HLA-mismatched HSCT for the treatment of pediatric solid tumors and the inherent preliminary results.

Human neuroblastoma cells rapidly enter cell cycle arrest and apoptosis following exposure to C-28 derivatives of the synthetic triterpenoid CDDO

Synthetic triterpenoids, such as 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and its derivatives, are an extremely potent class of new anti-cancer therapeutic agents, characterized by high anti-tumor potency and low toxicity to normal tissues. This report is the first to investigate the effects of C-28 derivatives of CDDO on 22 pediatric solid tumor cell lines, including neuroblastoma, rhabdomyosarcoma, osteosarcoma, and Ewing's sarcoma. We determined IC50s in the range of 5 – 170 nM for inhibition of colony formation and DNA synthesis, and 110 – 630 nM for metabolic cell death and decrease in cell number, using the C-28 CDDO analogs, CDDO methyl ester (CDDO-Me), CDDO imidazolide (CDDO-Im), CDDO ethyl amide (CDDO-EA), CDDO trifluoroethyl amide (CDDO-TFEA), and CDDO diethylamide (CDDO-DE). After treatment of human neuroblastoma cells with CDDO-Me, cell cycle studies show depletion of the S-phase, while apoptosis studies show conformational activation and mitochondrial translocation of Bax protein, as well as activation of caspases -3 and -8. These data demonstrate the potential utility of CDDO analogs as promising novel therapeutic agents for high-risk pediatric solid tumors.

Combined Biodifferentiating and Antiangiogenic Oral Metronomic Therapy is Feasible and Effective in Relapsed Solid Tumors in Children: Single-Center Pilot Study

To outline an outpatient-based treatmentfor children with relapsed solid tumors, who alreadyhave been extensively pretreated, we defined a 4-drugprotocol named COMBAT (combined oral maintenancebiodifferentiating and antiangiogenic therapy). Using thisprotocol, we performed a pilot study to determine its feasibilityin children with relapsed and/or high-risk pediatricsolid tumors. Patients and Methods: 22 children receivedthe COMBAT protocol. Treatment consisted ofdaily celecoxib administration along with daily 13-cisretinoicacid (2 weeks on / 2 weeks off) and cycles ofmetronomic temozolomide (90 mg/m2 for 42 days) andlow-dose etoposide (21 days). The treatment was scheduledfor a period of 1 year. Results: 9 of the 14 patientsassessable for response demonstrated evidence of treatmentbenefit manifested as prolonged disease stabilizationor response. The protocol medication was well toleratedwith very good compliance. Only minimal side effectswhere observed which responded to dose modificationor local therapy. Conclusions: The COMBATregimen is well tolerated by patients with intensive priortherapy including myeloablative regimens. Favorable responsesobserved in this cohort of patients support thefurther exploration of this and/or similar strategies in thetreatment of pediatric solid tumors.

Quimioterapia intensiva con soporte de progenitores hematopoyéticos en neoplasias sólidas no hematológicas de la edad pediátrica: indicaciones y estado actual del tema

High-dose chemotherapy with autologous bone marrow or peripheral stem cell support is frequently used for the treatment of high-risk pediatric solid tumors. The gained experience with these treatments runs parallel with a considerable decrease on the procedure-related complications. These strategies have demonstrated its efectivity in the treatment of high-risk neuroblastoma as well as in refractory or relapsed germ cell tumors. There are also evidences showing that its use in high-risk Ewing’s sarcoma, and in chemosensitive relapsed or metastatatic brain tumors, contributes to ameliorate the dismal prognosis of these patients.