Pediatric Bone Sarcomas Research Articles

Introducing Fluorescence-Guided Surgery for Pediatric Ewing, Osteo-, and Rhabdomyosarcomas: A Literature Review.

Sarcomas are a rare heterogeneous group of malignant neoplasms of mesenchymal origin which represent approximately 13% of all cancers in pediatric patients. The most prevalent pediatric bone sarcomas are osteosarcoma (OS) and Ewing sarcoma (ES). Rhabdomyosarcoma (RMS) is the most frequently occurring pediatric soft tissue sarcoma. The median age of OS and ES is approximately 17 years, so this disease is also commonly seen in adults while non-pleiomorphic RMS is rare in the adult population. The mainstay of all treatment regimens is multimodal treatment containing chemotherapy, surgical resection, and sometimes (neo)adjuvant radiotherapy. A clear resection margin improves both local control and overall survival and should be the goal during surgery with a curative intent. Real-time intraoperative fluorescence-guided imaging could facilitate complete resections by visualizing tumor tissue during surgery. This review evaluates whether non-targeted and targeted fluorescence-guided surgery (FGS) could be beneficial for pediatric OS, ES, and RMS patients. Necessities for clinical implementation, current literature, and the positive as well as negative aspects of non-targeted FGS using the NIR dye Indocyanine Green (ICG) were evaluated. In addition, we provide an overview of targets that could potentially be used for FGS in OS, ES, and RMS. Then, due to the time- and cost-efficient translational perspective, we elaborate on the use of antibody-based tracers as well as their disadvantages and alternatives. Finally, we conclude with recommendations for the experiments needed before FGS can be implemented for pediatric OS, ES, and RMS patients.

Noninvasive Expandable Endoprostheses From Reconstruction to Skeletal Maturity: A Surgical Technique and Lengthening Guide.

Limb salvage is the benchmark for pediatric extremity bone sarcomas. However, reconstructive strategies must account for any anticipated remaining growth potential and the resultant limb inequality. Expandable endoprostheses offer the theoretical advantage of immediate weight-bearing, predictable function, and reliable maintenance of leg-length equality. The evolution of the lengthening mechanism now permits noninvasive lengthening, opposed to the multiple open procedures of the past. These design improvements have contributed to their growing popularity. Experience has indicated that these noninvasive implants more reliably achieve leg-length equality, have longer failure-free survival, and decreased complications, although some have noted gearbox and lengthening failures. Currently, no standardize technique exists for managing patients with noninvasive expandable implants from the time of reconstruction to final lengthening at skeletal maturity. This blueprint aims to provide a detailed surgical technique, lengthening schedule, and recommendations for the mitigation and management of complications to achieve successful limb salvage with noninvasive expandable endoprostheses.

Pattern of Pediatric Soft Tissue and Bone Sarcomas at South Egypt Cancer Institute, Retrospective Study

Pattern of Pediatric Soft Tissue and Bone Sarcomas at South Egypt Cancer Institute, Retrospective Study

Extracorporeal Irradiation in Pediatric Bone Sarcomas

Extracorporeal irradiation (ECI) consists of en bloc removal of the tumor bearing bone segment, removal of the tumor from the bone, irradiation and reimplantation back in the body. ECI is mostly used in adult bone sarcomas. It is extremely rare method of treatment used in the management of pediatric bone sarcomas (PBS). We report our preliminary experience of using ECI for management of PBS. Our study is based on the data of 28 patients with primary PBS who were treated with ECI. The eligibility criteria for patient enrollment included histopathological proof of malignancy, no evidence of distant metastases, and suitability for limb preservation therapy. Surgery was performed about 4 weeks after completion of standard neoadjuvant chemotherapy. The affected bone segment was resected, irradiated extracorporeally with a dose of 50 Gy and reimplanted. Local control, complications and short-term survival were studied. Functional outcome was assessed by Musculoskeletal Tumor Society (MSTS) scoring system. There were 21 males and 7 females with median age of 11 years (range 2-18 years). Histopathologically, 16 had Ewing’s sarcoma family of tumors (ESFT) and 12 patients had osteosarcoma (OS). Distribution of primary site was as follows: femur 18, tibia 8 and others 2. Follow-up period ranged from 5-31 months. At a median follow-up was 19 months, 6 patients (2 OS, 1 ESFT) had systemic relapse as well as local recurrence (LR). No patient had isolated local recurrence. The 2-year disease free survival was 71% and mean MSTS score was 88. Three patients (11%) developed wound infection in the perioperative period. Results of our study suggest that ECI is feasible in the management of PBS and provides decent local control and disease-free survival rates.

Chimeric Antigen Receptor-modified T cells targeting EphA2 for the immunotherapy of paediatric bone tumours

Chimeric Antigen Receptor (CAR) T-cell therapy, as an approved treatment option for patients with B cell malignancies, demonstrates that genetic modification of autologous immune cells is an effective anti-cancer regimen. Erythropoietin-producing Hepatocellular receptor tyrosine kinase class A2 (EphA2) is a tumour associated antigen expressed on a range of sarcomas, including paediatric osteosarcoma (OS) and Ewing sarcoma (ES). We tested human EphA2 directed CAR T cells for their capacity to target and kill human OS and ES tumour cells using in vitro and in vivo assays, demonstrating that EphA2 CAR T cells have potent anti-tumour efficacy in vitro and can eliminate established OS and ES tumours in vivo in a dose and delivery route dependent manner. Next, in an aggressive metastatic OS model we demonstrated that systemically infused EphA2 CAR T cells can traffic to and eradicate tumour deposits in murine livers and lungs. These results support further pre-clinical evaluation of EphA2 CAR T cells to inform the design of early phase clinical trial protocols to test the feasibility and safety of this immune cell therapy in paediatric bone sarcoma patients.

Abstract 1950: The eIF4A inhibitors didesmethylrocaglamide and rocaglamide as effective treatments for pediatric bone and soft-tissue sarcomas

Abstract Background: Development of an effective medical therapy for osteosarcoma and Ewing sarcoma, the two most common aggressive forms of pediatric bone and soft-tissue sarcomas, is urgently needed as current treatments are inadequate particularly for those with recurrent or metastatic diseases. To achieve this goal, we have identified two natural eIF4A inhibitors, rocaglamide (Roc) and didesmethylrocaglamide (DDR), which potently inhibit proliferation of a series of commonly-used osteosarcoma and Ewing sarcoma cell lines. We also demonstrated that Roc effectively suppresses tumor growth in patient-derived xenograft (PDX) models of osteosarcoma and Ewing sarcoma. Both Roc- and DDR-treated sarcoma cells show decreased levels of multiple oncogenic kinases, including insulin-like growth factor-1 receptor (IGF-1R). Importantly, these rocaglamides are not sensitive to multidrug resistance 1 (MDR1) efflux. In addition, Roc exhibits 50% oral bioavailability, is well-tolerated in mice, and does not induce pulmonary toxicity in dogs as found with another eIF4A inhibitor silvestrol (Chang et al. Mol Cancer Ther. 2019; In Revision). Methods: Various osteosarcoma and Ewing sarcoma cell lines were treated with DDR and Roc, followed by cell proliferation assay, flow cytometry, and immunoblotting. Mesenchymal stem cells (MSCs) were used as a control for comparing the expression levels of the eIF4F components important for translation initiation. RNA interference (RNAi) and CRISPR/Cas9 techniques were used to verify eIF4A dependency. An orthotopic cell line-derived xenograft (CDX), a metastatic xenograft, and a PDX models for osteosarcoma and immunohistochemistry were used to assess antitumor efficacy. Results: We hypothesize that osteosarcoma and Ewing sarcoma cells are highly addicted to active protein synthesis and that Roc and DDR, by acting as potent eIF4A inhibitors with an ability to induce apoptosis and the DNA damage response, effectively eliminate these malignant sarcomas. We found that various osteosarcoma and Ewing sarcoma cell lines expressed higher levels of eIF4A2, but not eIF4A1, eIF4E, and eIF4G, than MSCs, suggesting a role of eIF4A2 in enhancing protein translation in these sarcoma cells. RNAi knockdown and CRISPR/Cas9 knockout experiments are being evaluated to verify this finding. Both DDR and Roc effectively blocked tumor growth in an orthotopic CDX model. As found with Roc previously, DDR also potently inhibited the growth of an osteosarcoma PDX model. Both rocaglamides were well tolerated at 3 mg/kg by IP every other day and did not cause any significant changes in body weight, compared with vehicle-treated controls. We are presently determining the effects of Roc and DDR on osteosarcoma metastasis. Conclusions: The potent anti-tumor activity and favorable toxicity profile of Roc and DDR suggest that these rocaglamides should be further evaluated as potential treatments for osteosarcomas and Ewing sarcomas. Citation Format: Long-Sheng Chang, Janet L. Oblinger, Garima Agarwal, Tyler A. Wilson, Ryan Roberts, James Fuchs, Barry R. O'Keefe, A. Douglas Kinghorn, Jerry M. Collins. The eIF4A inhibitors didesmethylrocaglamide and rocaglamide as effective treatments for pediatric bone and soft-tissue sarcomas [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1950.

Bisphosphonates in common pediatric and adult bone sarcomas

The therapeutic strategies proposed currently for bone sarcomas are based on neo-adjuvant chemotherapy, delayed en-bloc wide resection, and adjuvant chemotherapy. Unfortunately, bone sarcomas are characterized by high rates of poor drug response, with a high risk of drug resistance, local recurrence and/or a high propensity for induced metastases. The pathogenesis of bone sarcomas is strongly associated with dysregulation of local bone remodeling and increased osteolysis that plays a part in tumor development. In this context, bisphosphonates (BPs) have been proposed as a single agent or in combination with conventional drugs to block bone resorption and the vicious cycle established between bone and sarcoma cells. Pre-clinical in vitro studies revealed the potential "anti-tumor" activities of nitrogen-bisphosphonates (N-BPs). In pre-clinical models, N-BPs reduced significantly primary tumor growth in osteosarcoma and Ewing sarcoma, and the installation of lung metastases. In chondrosarcoma, N-BPs reduced the recurrence of local tumors after intralesional curettage, and increased overall survival. In pediatric and adult osteosarcoma patients, N-BPs have been assessed in combination with conventional chemotherapy and surgery in randomized phase 3 studies with no improvement in clinical outcome. The lack of benefit may potentially be explained by the biological impact of N-BPs on macrophage differentiation/recruitment which may alter CD8+-T lymphocyte infiltration. Thanks to their considerable affinity for the mineralized extracellular matrix, BPs are an excellent platform for drug delivery in malignant bone sites with reduced systemic toxicity, which opens up new opportunities for their future use.

Hippo/YAP Signaling Pathway: A Promising Therapeutic Target in Bone Paediatric Cancers?

Osteosarcoma and Ewing sarcoma are the most prevalent bone pediatric tumors. Despite intensive basic and medical research studies to discover new therapeutics and to improve current treatments, almost 40% of osteosarcoma and Ewing sarcoma patients succumb to the disease. Patients with poor prognosis are related to either the presence of metastases at diagnosis or resistance to chemotherapy. Over the past ten years, considerable interest for the Hippo/YAP signaling pathway has taken place within the cancer research community. This signaling pathway operates at different steps of tumor progression: Primary tumor growth, angiogenesis, epithelial to mesenchymal transition, and metastatic dissemination. This review discusses the current knowledge about the involvement of the Hippo signaling pathway in cancer and specifically in paediatric bone sarcoma progression.

SHH Signaling Pathway Drives Pediatric Bone Sarcoma Progression.

Primary bone tumors can be divided into two classes, benign and malignant. Among the latter group, osteosarcoma and Ewing sarcoma are the most prevalent malignant primary bone tumors in children and adolescents. Despite intensive efforts to improve treatments, almost 40% of patients succumb to the disease. Specifically, the clinical outcome for metastatic osteosarcoma or Ewing sarcoma remains poor; less than 30% of patients who present metastases will survive 5 years after initial diagnosis. One common and specific point of these bone tumors is their ability to deregulate bone homeostasis and remodeling and divert them to their benefit. Over the past years, considerable interest in the Sonic Hedgehog (SHH) pathway has taken place within the cancer research community. The activation of this SHH cascade can be done through different ways and, schematically, two pathways can be described, the canonical and the non-canonical. This review discusses the current knowledge about the involvement of the SHH signaling pathway in skeletal development, pediatric bone sarcoma progression and the related therapeutic options that may be possible for these tumors.

Thirty-Day Outcomes following Pediatric Bone and Soft Tissue Sarcoma Surgery: A NSQIP Pediatrics Analysis.

Background Pediatric bone and soft tissue sarcomas are rare; therefore, national registries are essential tools for orthopedic oncology research. Past studies provide excellent data on long-term prognosis and survival trends but fail to examine treatment-specific morbidity. The aim of this study is to use a national registry to describe patient demographics, comorbidities, and adverse events in the first thirty days following surgical management of pediatric bone and soft tissue sarcomas. Methods A retrospective review of patients in the American College of Surgeons National Surgical Quality Improvement Program—Pediatrics database (NSQIP-P) was performed. The cohort was partitioned by tumor origin (bone versus soft tissue) and tumor location (axial versus appendicular). Results One-hundred ninety-two patients were identified. Bone sarcomas were more common (71.9%) and predominately appendicular (62.3%), while soft tissue sarcomas were predominately axial (77.8%). The overall complication rate was 8.9%. The most frequent etiologies were wound dehiscence (3.6%) and infectious complications such as surgical site infections (2.6%), pneumonia (1.6%), urinary tract infections (1.6%), and C. diff colitis (1.0%). Twenty-four percent of patients experienced bleeding requiring transfusion. The unplanned readmission rate was 12.5% (3.6% related to principle procedure), and the unplanned reoperation rate was 4.7% (4.2% related to principle procedure). The mortality rate was 1.0%. Neoadjuvant chemotherapy was associated with higher rates of wound dehiscence and infectious complications. There were no differences in adverse events with respect to tumor origin or location. Conclusion Approximately 1 in 11 pediatric patients will experience a complication in the first thirty days following surgery. However, perioperative mortality remains low. This study represents the first comprehensive review of pediatric bone and soft tissue sarcoma surgery in the NSQIP-P database. As the case volume of NSQIP-P continues to grow, NSQIP-P has the potential to become a powerful tool for pediatric orthopedic oncology research.

Omic approaches to pediatric bone sarcomas.

Over the last decade, next-generation sequencing technologies have improved our ability to assess biological aspects, at genomic and transcriptomic levels, on a large scale- and have been increasingly used for the management of adult cancers. However, their efficacy and feasibility within pediatrics is still under investigation. "Omic" approaches represent an opportunity to understand the oncogenic mechanisms driving the onset and progression of bone sarcoma and improve the clinical management of young patients with bone sarcomas. This review focuses on the current genomic and transcriptomic characteristics of managing pediatric patients, affected by Ewing sarcoma and osteosarcoma.

Pediatric extremity bone sarcoma reconstruction with the vascularized fibula flap: Observational study assessing long-term functional outcomes, complications, and survival

BackgroundLimb salvage is important in pediatric patients with bone sarcomas. The vascularized fibula flap is a versatile option, combined or not with a bone allograft. The authors evaluated the functional long-term outcomes, complications, and survival of using this technique in pediatric patients. MethodsA retrospective review of 27 pediatric patients reconstructed between 2011 and 2018 with the fibula flap after bone sarcoma resection was conducted. Long-term functional outcomes, complications, and survival were assessed. Variables analyzed were age, sex, Capanna technique, follow-up, complications, additional surgeries, time to weight bearing, length discrepancy, and sport practice. ResultsTwenty-seven patients with a mean age of 9.3 years were included. The mean follow-up was 44.33 months. The Capanna technique was performed in 15 patients. All extremities but one were salvaged. The overall complication rate was 74.07%. Fibula fracture and nonunion rates were 34.04% and 11.11%, respectively. Partial weight bearing was resumed at a mean of 9.07 months. About 79.17% of patients with a 12-month follow-up achieved full weight bearing.An age below 8 years was significantly associated with a lower major complication rate and a shorter time to weight bearing and full weight bearing. Major complications and additional surgeries were significantly associated with longer periods until weight bearing and full weight bearing. ConclusionsThe fibula flap allows the majority of extremities to be reconstructed. However, a high rate of complications and additional surgeries should be anticipated. Full weight bearing is usually achieved within the first year, with modest functional increase afterward. Less complications and a faster functional recovery are expected in patients below the age of 8 years.

Pediatric Bone Sarcomas: Outcome of Multimodality Treatment in a Single Institution in South India over a Decade

Abstract Context: Pediatric bone sarcoma is a rare entity with low incidence of around 2.5–6 per million population in India. Management of this condition is well standardized, and global survival data are available; however, there is a paucity of data in the Indian perspective. Aim of the Study: The aim of this study is to analyze various prognostic factors and survival outcome. The purpose of this study is to assess the role of surgery, multiagent chemotherapy, and radiation in the management of these tumors. Patients and Methods: Retrospective analysis of patients aged 18 and less, diagnosed as bone sarcomas and treated in our tertiary cancer center. All the patients received at least one form of therapy depending on stage and site of the primary lesion. Results: Twenty-one patients of Ewing sarcoma and 20 patients of osteosarcomas were eligible and were included in the study. In Ewing sarcoma, completing the full course of standard chemotherapy and radiotherapy to the local site was associated with improved survival. In osteosarcoma, limb salvage surgery (LSS) had a significant difference in overall survival compared to amputation. Induction chemotherapy was associated with better percentage of necrosis and showed improved survival. The percentage of necrosis correlated positively with survival which was statistically significant (P = 0.015). Conclusion: The median survival in both these bone sarcomas is inferior to global trends. Probable reasons for such discrepancy are lack of compliance to treatment protocols due to age factors and late presentation. Completion of multiagent chemotherapy in both the tumors add to better survival. Radiotherapy in Ewing sarcoma improves survival. In osteosarcoma, LSS is an oncologically safe alternative to amputation. The percentage of necrosis following chemotherapy in osteosarcoma is a reliable predictor of prognosis.

Pediatric Soft Tissue and Bone Sarcomas in Tanzania: Epidemiology and Clinical Features.

PURPOSEPediatric sarcomas represent an important group of childhood tumors that require treatment at Muhimbili National Hospital (MNH), the largest pediatric oncology center in Tanzania. Treatment is often adapted from established childhood protocols validated in clinical trials from the United States and the United Kingdom. There are no studies describing the types of pediatric sarcomas most commonly seen in Tanzania to understand similarities and disparities with other countries and which sarcomas to prioritize in adapting treatment protocols. The objective of this study was to establish a baseline of the epidemiologic and clinical features of pediatric sarcomas diagnosed at MNH.METHODSInformation was collected on clinical and tumor features of all children seen at MNH pediatric oncology unit between 2011 and 2016 with a confirmed histologic diagnosis of either bone or soft tissue sarcoma (STS).RESULTSA total of 135 cases were analyzed; 89 (66%) were STS and 46 (34%) were bone sarcomas. There was a slight female predominance (n = 69; 51%), and the mean age (SD) of patients was 6.3 (5.1) years. Greater than 90% (n = 123) of the cases presented with a painless swelling. The commonest STS, accounting for almost three-fourths of the cases (n = 66) was rhabdomyosarcoma (RMS), with embryonal subtype being the most common RMS (n = 49; 74%). Osteosarcoma was the most common bone sarcoma, accounting for greater than 80% (n = 40) of the cases. Ewing sarcoma accounted for less than 15% (n = 6). Most of the patients presented with stage IV disease (n = 57; 87%) and lung was the commonest metastatic site.CONCLUSIONTo our knowledge, this report is the first study documenting the epidemiologic and clinical features of pediatric sarcomas in a modern Tanzanian pediatric hospital. Embryonal RMS and osteosarcomas should be prioritized for adapting treatment protocols from other countries.

Integration of genomic copy number variations and chemotherapy-response biomarkers in pediatric sarcoma

BackgroundWhile most pediatric sarcomas respond to front-line therapy, some bone sarcomas do not show radiographic response like soft-tissue sarcomas (rhabdomyosarccomas) but do show 90% necrosis. Though, new therapies are urgently needed to improve survival and quality of life in pediatric patients with sarcomas. Complex chromosomal aberrations such as amplifications and deletions of DNA sequences are frequently observed in pediatric sarcomas. Evaluation of copy number variations (CNVs) associated with pediatric sarcoma patients at the time of diagnosis or following therapy offers an opportunity to assess dysregulated molecular targets and signaling pathways that may drive sarcoma development, progression, or relapse. The objective of this study was to utilize publicly available data sets to identify potential predictive biomarkers of chemotherapeutic response in pediatric Osteosarcoma (OS), Rhabdomyosarcoma (RMS) and Ewing’s Sarcoma Family of Tumors (ESFTs) based on CNVs following chemotherapy (OS n = 117, RMS n = 64, ESFTs n = 25 tumor biopsies).MethodsThere were 206 CNV profiles derived from pediatric sarcoma biopsies collected from the public databases TARGET and NCBI-Gene Expression Omnibus (GEO). Through our comparative genomic analyses of OS, RMS, and ESFTs and 22,255 healthy individuals called from the Database of Genomic Variants (DGV), we identified CNVs (amplifications and deletions) pattern of genomic instability in these pediatric sarcomas. By integrating CNVs of Cancer Cell Line Encyclopedia (CCLE) identified in the pool of genes with drug-response data from sarcoma cell lines (n = 27) from Cancer Therapeutics Response Portal (CTRP) Version 2, potential predictive biomarkers of therapeutic response were identified.ResultsGenes associated with survival and/recurrence of these sarcomas with statistical significance were found on long arm of chromosome 8 and smaller aberrations were also identified at chromosomes 1q, 12q and x in OS, RMS, and ESFTs. A pool of 63 genes that harbored amplifications and/or deletions were frequently associated with recurrence across OS, RMS, and ESFTs. Correlation analysis of CNVs from CCLE with drug-response data of CTRP in 27 sarcoma cell lines, 33 CNVs out of 63 genes correlated with either sensitivity or resistance to 17 chemotherapies from which actionable CNV signatures such as IGF1R, MYC, MAPK1, ATF1, and MDM2 were identified. These CNV signatures could potentially be used to delineate patient populations that will respond versus those that will not respond to a particular chemotherapy.ConclusionsThe large-scale analyses of CNV-drug screening provides a platform to evaluate genetic alterations across aggressive pediatric sarcomas. Additionally, this study provides novel insights into the potential utilization of CNVs as not only prognostic but also as predictive biomarkers of therapeutic response. Information obtained in this study may help guide and prioritize patient-specific therapeutic options in pediatric bone and soft-tissue sarcomas.

Abstract A42: Prexasertib (LY2606368) is highly active as a monotherapy or in combination with chemotherapy in preclinical models of pediatric bone and soft tissue sarcoma

Abstract The serine/threonine kinase checkpoint kinase 1 (CHK1) is a crucial mediator of replication stress and helps maintain genome integrity by governing the S-phase and G2/M cell cycle checkpoints following DNA damage, facilitating DNA repair through homologous recombination, and licensing replication forks during S phase. The CHK1 small-molecule inhibitor prexasertib (LY2606368) is currently under clinical investigation in pediatric cancer patients with recurrent or refractory solid tumors (NCT02808650). Reduced proliferation was observed at low nanomolar concentrations in a panel of pediatric bone and soft tissue sarcoma cell lines. In addition, prexasertib caused DNA damage and cell death in vitro as measured by Western blot analysis and high content imaging. Prexasertib as a monotherapy was superior to doxorubicin or actinomycin D in several cell line-derived and patient-derived xenograft (PDX) models of pediatric soft tissue sarcoma, with two models of alveolar rhabdomyosarcoma (aRMS) demonstrating a complete response to prexasertib; however, acquired resistance to prexasertib was observed. In addition, preclinical PDX mouse models of Ewing’s sarcoma and osteosarcoma typically demonstrated intrinsic resistance to single-agent prexasertib. Importantly, combination with cytotoxic chemotherapy could not only overcome intrinsic prexasertib resistance in vivo, as would be expected given the potential for prexasertib to act as a chemopotentiator, but also prevented the emergence of acquired resistance following single-agent prexasertib treatment. In vitro experiments were performed to evaluate the effect of prexasertib plus chemotherapy on cell proliferation. Future preclinical studies include genomic analysis of pediatric bone and soft tissue sarcoma models to delineate the molecular underpinnings of sensitivity and acquired resistance to prexasertib and to identify predictive biomarkers for response. Citation Format: Caitlin D. Lowery, Wayne Blosser, Michele Dowless, Matthew Renschler, Jennifer Stephens, Richard Beckmann, Louis Stancato. Prexasertib (LY2606368) is highly active as a monotherapy or in combination with chemotherapy in preclinical models of pediatric bone and soft tissue sarcoma [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr A42.

Use of Vascularized Fibular Free Flap in the Reconstruction of the Femur in Pediatric and Adolescent Bone Sarcomas: Complications and Functional Outcome.

Most reports on skeletal reconstruction using vascularized fibular free flap include patients with varying age groups and anatomic locations. This study has limited the inclusion criteria to pediatric and adolescent patients diagnosed with bone sarcoma of the femoral shaft. Forty-one patients, diagnosed with a malignant bone tumor of the femoral shaft (21 Ewing's sarcomas and 20 osteosarcomas), were locally treated by joint sparing wide resection and reconstruction using a vascularized fibular free flap. All clinical and radiographic data were reviewed for graft healing and hypertrophy as well as oncologic and functional outcome. The mean follow-up period was 48.7 months (12-104 months). The mean age at presentation was 10.3 years (5-17 years). The average length of the resected femoral shaft was 19.2 cm (15-24 cm) and the average length of the harvested fibula was 17.4 cm (15-21 cm). The mean time to union was 4.8 months (1-6 months) and the mean hypertrophy index was 78% (15.5-184%). Complications included 12 fractures (33.3%), 5 non-unions (13.8%), and 5 failures of graft hypertrophy (13.8%). At the latest clinical evaluation, the mean MSTS score was 81% (56-100%) and the mean limb length inequality was 4.75 cm (3-11 cm). Despite the high functional demand and deleterious effect of chemotherapy on bone healing, reconstruction of the femur by vascularized fibular free flap in pediatric bone sarcomas can lead to a good functional outcome. Complications, such as fracture and non-union, can be successfully treated by revision of fixation and autologous iliac crest grafting. IV.

CORR Insights®: MRI Identification of the Osseous Extent of Pediatric Bone Sarcomas.

CORR Insights®: MRI Identification of the Osseous Extent of Pediatric Bone Sarcomas.

Anthracycline-induced cardiotoxicity in patients with paediatric bone sarcoma and soft tissue sarcoma.

Anthracycline cardiotoxicity is an important side-effect in long-term childhood cancer survivors. We evaluated the incidence of and factors associated with anthracycline cardiotoxicity in a population of patients diagnosed with bone or soft tissue sarcoma. Materials and methods We retrospectively enrolled patients diagnosed with bone or soft tissue sarcoma, from 1995 to 2011, treated with anthracycline chemotherapy at our Centre and with a follow-up echocardiography carried out ⩾3 years from cardiotoxic therapy completion. Cardiac toxicity was graded using Common Terminology Criteria for Adverse Events version 4.0. A total of 82 patients were eligible. The median age at treatment was 11.9 years (1.44-18). We evaluated the median cumulative anthracycline dose, age at treatment, sex, thoracic radiotherapy, hematopoietic stem cell transplantation, and high-dose cyclophosphamide treatment as possible risk factors for cardiotoxicity. The median cumulative anthracycline dose was 390.75 mg/m2 (80-580). Of the 82 patients, 12 (14.6%) developed cardiotoxicity with grade ⩾2 ejection fraction decline: four patients were asymptomatic and did not receive any treatment; six patients were treated with pharmacological heart failure therapy; one patient with severe cardiomyopathy underwent heart transplantation and did not need any further treatment; and one patient died while waiting for heart transplantation. The median time at cardiac toxicity, from the end of anthracycline frontline chemotherapy, was 4.2 years (0.05-9.6). Cumulative anthracycline dose ⩾300 mg/m2 (p 0.04) was the only risk factor for cardiotoxicity on statistical analyses. In our population, the cumulative incidence of cardiotoxicity is comparable to rates in the literature. This underlines the need for primary prevention and lifelong cardiac toxicity surveillance programmes in long-term childhood cancer survivors.

Abstract 5825: Mechanisms of intrinsic and acquired resistance to antibodies targeting IGF-1R in pediatric sarcoma cell lines

Abstract Background: Pediatric bone and soft tissue sarcomas are heavily dependent on the Type 1 insulin-like growth factor receptor (IGF-1R) signaling axis, which promotes tumorigenic properties such as proliferation, survival, angiogenesis and metastasis. While a substantial proportion of patients demonstrate intrinsic resistance to monoclonal antibodies targeting IGF-1R, a strong and sustained response is seen in a limited number of patients, and disease stabilization in about 30% of patients. Understanding these resistance mechanisms may identify combinations of targeted therapies that optimize therapeutic efficiency of IGF-1R-targeted antibodies. Methods: For intrinsic resistance, we used a panel of Ewing sarcoma (ES; n=10) and rhabdomyosarcoma (RMS; n=10) cell lines that, with the exception of Rh41, are all intrinsically resistant to TZ-1, a monoclonal antibody that targets IGF-1R. For acquired resistance, we developed a TZ-1 resistant RMS cell line, Rh41/TZ-1. We utilized Receptor Tyrosine Kinase (RTK) Arrays to analyze the phosphorylation status of 49 RTKs. The cell lines were treated with TZ-1 and changes in RTK expression were assessed by quantitative PCR. Results: RMS cells intrinsically resistant to TZ-1 treatment expressed multiple activated RTKs including EGFR family of receptors, IGF-1R, IR, PDGFR, FGFR4, HGFR4, RYK, ALK, DDR1, AXL, DTK. Interestingly, ES cells (n=5) had either a complex pattern of activated RTK expression similar to RMS cells or a relatively less complex set (n=5) of activated RTKs (IGF-1R, IR, HGFR, ERBB4, AXL, DTK). TZ-1 treatment of these cell lines with intrinsic resistance demonstrated decreased phosphorylation of IGF-1R, but had little effect on other RTKs. In contrast TZ-1 treatment of Rh41 cells rapidly induced activation of several RTKs including: AXL, PDGFRB, FGFR4 and ALK. Increased expression of these receptors was confirmed by qPCR. In contrast, Rh41/TZ-1 cells selected for acquired resistance to TZ-1 constitutively expressed activated RTKs (PDGFRB, FGFR4, AXL, DTK, VEGFR1). In Rh41 cells treated with TZ-1, the BRD4 inhibitor, JQ1 (500 nM, 24 Hr), blocked the induction of IGF-1R, IRB, AXL, PDGFR-A/-B, VEGFR1 and ALK. However, it had less effect on the induction of FGFR 2/3/4 receptors. Further, combined treatment of TZ-1 and JQ1 reduced cellular proliferation of Rh41 cells more than TZ-1 treatment alone. Conclusions: We demonstrate that intrinsic resistance to the IGF-1R targeted antibody TZ-1 is characterized by constitutive activation of multiple RTKs. In response to TZ-1 treatment in a sensitive cell line there is rapid induction of multiple RTKs indicating a dynamic response to inhibition of IGF-1R. Our data suggests that BRD4 is involved in induction of these signaling molecules and that combined inhibition of BRD4 along with the IGF-1R targeted therapy can overcome this resistance and warrants further investigation. Support: US Public Health Service Grant CA165995. Citation Format: Terry J. Shackleford, Seethalakshmi Hariharan, Doris Phelps, Hemant Bid, Hiahong Zhong, Peter Houghton. Mechanisms of intrinsic and acquired resistance to antibodies targeting IGF-1R in pediatric sarcoma cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5825. doi:10.1158/1538-7445.AM2017-5825