Consensus recommendations in the management of Ewing sarcoma from the National Ewing Sarcoma Tumor Board

Ewing sarcoma (ES) is a malignant tumor of bone and soft tissue that most often occurs in adolescents and young adults. Despite an international coordinated approach, several nuances, discrepancies, and debates remain in defining the standard of care for treating ES. In this review, the authors leverage the expertise assembled by formation of the National Ewing Sarcoma Tumor Board, a multi-institution, multidisciplinary virtual tumor board that meets monthly to discuss complicated and challenging cases of ES. This report is focused on select topics that apply to the management of patients with newly diagnosed ES. The specific topics covered include indications for bone marrow aspirate and biopsy for initial evaluation compared with fluorodeoxyglucose-positron emission tomography, the role of interval compressed chemotherapy in patients aged 18 years and older, the role of adding ifosfamide/etoposide to vincristine/doxorubicin/cyclophosphamide for patients with metastatic disease, the data on and role of high-dose chemotherapy with autologous stem cell transplantation, maintenance therapy, and whole-lung irradiation. The data referenced are often limited to subgroup analyses and/or compiled from multiple sources. Although not intended to replace the clinical judgement of treating physicians, the guidelines are intended to provide clarity and recommendations for the upfront management of patients with ES. PLAIN LANGUAGE SUMMARY: Ewing sarcoma is a malignant tumor of bone and soft tissue that most often occurs in adolescents and young adults. For this review, the authors used the experience of the National Ewing Sarcoma Tumor Board, a multi-institution, multidisciplinary virtual tumor board that meets monthly to discuss complicated and challenging cases of Ewing sarcoma. Although not intended to replace the clinical judgement of treating physicians, the guidelines will focus on the development of consensus statements for the upfront management of patients with Ewing sarcoma.

Osteosarcoma in Pediatric and Adult Populations: Are Adults Just Big Kids?

Malignant bone tumors are commonly classified as pediatric or adolescent malignancies, and clinical trials for these diseases have generally focused on these populations. Of primary bone cancers, osteosarcoma is among the most common. Osteosarcoma has a bimodal age distribution, with the first peak occurring in patients from 10 to 14 years old, and the second peak occurring in patients older than 65, with about 25% of cases occurring in adults between 20 and 59 years old. Notably, adult osteosarcoma patients have worse outcomes than their pediatric counterparts. It remains unclear whether age itself is a poor prognostic factor, or if inherent differences in tumor biology exist between age groups. Despite these unknowns, current treatment strategies for adults are largely extrapolated from pediatric studies since the majority of clinical trials for osteosarcoma treatments are based on younger patient populations. In light of the different prognoses observed in pediatric and adult osteosarcoma, we summarize the current understanding of the molecular etiology of osteosarcoma and how it may differ between age groups, hypothesizing why adult patients have worse outcomes compared to children.

CD43-positive, EWSR1::FLI1 -rearranged Soft Tissue Sarcoma in a Pediatric Patient With History of B-Cell Acute Lymphoblastic Leukemia

Ewing sarcoma is a small round blue cell tumor typically characterized by an EWSR1 rearrangement and expression of CD99 and NKX2.2, without expression of hematopoietic markers such as CD45. CD43 is an alternative hematopoietic immunohistochemical marker often utilized in the workup of these tumors and its expression typically argues against Ewing sarcoma. We report a 10-year-old with history of B-cell acute lymphoblastic leukemia presenting with an unusual malignant shoulder mass with variable CD43 positivity, but with an EWSR1::FLI1 fusion detected by RNA sequencing. Her challenging workup highlights the utility of next-generation DNA-based and RNA-based sequencing methods in cases with unclear or conflicting immunohistochemical results.

Intraventricular B7-H3 CAR T Cells for Diffuse Intrinsic Pontine Glioma: Preliminary First-in-Human Bioactivity and Safety

Diffuse intrinsic pontine glioma (DIPG) remains a fatal brainstem tumor demanding innovative therapies. As B7-H3 (CD276) is expressed on central nervous system (CNS) tumors, we designed B7-H3-specific chimeric antigen receptor (CAR) T cells, confirmed their preclinical efficacy, and opened BrainChild-03 (NCT04185038), a first-in-human phase I trial administering repeated locoregional B7-H3 CAR T cells to children with recurrent/refractory CNS tumors and DIPG. Here, we report the results of the first three evaluable patients with DIPG (including two who enrolled after progression), who received 40 infusions with no dose-limiting toxicities. One patient had sustained clinical and radiographic improvement through 12 months on study. Patients exhibited correlative evidence of local immune activation and persistent cerebrospinal fluid (CSF) B7-H3 CAR T cells. Targeted mass spectrometry of CSF biospecimens revealed modulation of B7-H3 and critical immune analytes (CD14, CD163, CSF-1, CXCL13, and VCAM-1). Our data suggest the feasibility of repeated intracranial B7-H3 CAR T-cell dosing and that intracranial delivery may induce local immune activation.

SIGNIFICANCE

This is the first report of repeatedly dosed intracranial B7-H3 CAR T cells for patients with DIPG and includes preliminary tolerability, the detection of CAR T cells in the CSF, CSF cytokine elevations supporting locoregional immune activation, and the feasibility of serial mass spectrometry from both serum and CSF. This article is highlighted in the In This Issue feature, p. 1.

Case report of congenital methemoglobinemia: an uncommon cause of neonatal cyanosis

Background

Methemoglobinemia can be an acquired or congenital condition. The acquired form occurs from exposure to oxidative agents. Congenital methemoglobinemia is a rare and potentially life-threatening cause of cyanosis in newborns that can be caused by either cytochrome B₅ reductase or hemoglobin variants known as Hemoglobin M.

Case presentation

A term male infant developed cyanosis and hypoxia shortly after birth after an uncomplicated pregnancy, with oxygen saturations persistently 70–80% despite 1.0 FiO2 and respiratory support of CPAP+ 6 cm H2O. Pre- and post-ductal saturations were equal and remained below 85%. Initial radiographic and echography imaging was normal. Capillary blood gas values were reassuring with normal pH and an elevated pO2. Investigations to rule out hemolysis and end-organ dysfunction were within acceptable range. Given the absence of clear cardiac or pulmonary etiology of persistent cyanosis, hematologic causes such as methemoglobinemia were explored. No family history was available at the time of transfer to our institution. Unconjugated hyperbilirubinemia > 5 mg/dL (442 μmol/L) interfered with laboratory equipment measurement, making accurate methemoglobin levels unattainable despite multiple attempts. Initial treatment with methylene blue or ascorbic acid was considered. However, upon arrival of the presumed biological father, a thorough history revealed an extensive paternal family history of neonatal cyanosis due to a rare mutation resulting in a hemoglobin M variant. Given this new information, hematology recommended supportive care as well as further testing to confirm the diagnosis of congenital methemoglobinopathy. Whole genome sequencing revealed a likely pathogenic variation in hemoglobin. The neonate was discharged home at 2 weeks of age on full oral feeds with 0.25 L/min nasal cannula as respiratory support, with close outpatient follow-up. By 5 weeks of age, he was weaned off respiratory support.

Conclusion

Congenital methemoglobinemia should be considered in the differential diagnosis for newborns with persistent hypoxemia despite normal imaging and laboratory values. Accurate quantification of methemoglobin concentrations is challenging in neonates due to the presence of other substances that absorb light at similar wavelengths, including HbF, bilirubin, and lipids.

Phase 1/2 study of devimistat in combination with hydroxychloroquine (HCQ) in patients with relapsed or refractory (R/R) clear cell sarcoma (CCS)

TPS11595

Background: CCS of the soft tissues is a rare and aggressive subtype of sarcoma that often starts in the tendons of the arms or legs. It is molecularly characterized by t(12;22)(q13;q12) translocation, resulting in EWSR1-ATF1 or EWSR1-CREB1 gene fusion. Despite reports of occasional responses to systemic therapies, currently available therapies have shown limited efficacy in advanced CCS. Therefore, there is a significant unmet medical need for more active agents in CCS. Devimistat is a stable intermediate of a lipoate analog that inhibits pyruvate dehydrogenase and α-ketoglutarate dehydrogenase enzymes of the tricarboxylic acid (TCA) cycle preferentially within the mitochondria of cancer cells. Devimistat induces autophagy in cancer cells. In a metastatic mouse model of CCS, treatment with devimistat in combination with chloroquine significantly suppressed tumor growth (Egawa et al, 2018). Based on this data, we hypothesized that inhibition of autophagy with HCQ may sensitize cancer cells to devimistat with increased efficacy and acceptable toxicity. Given its expected synergy, we have initiated a single-arm phase I/II prospective, multicenter, open-label, non-randomized study to evaluate maximally tolerated dose (MTD), safety, and efficacy of devimistat in combination with HCQ in patients with R/R CCS. Methods: In the phase 1 portion of the study, patients with R/R CCS and other fusion-positive R/R sarcomas will be enrolled and a standard 3+3 design will be followed to evaluate toxicity, MTD, and recommended phase 2 dose. There will be two patient groups based on weight, and dose escalation will be conducted separately for each group. Starting dose of HCQ will be 5mg/kg PO BID for patients < 45 kg and 200 mg PO BID for patients ≥45 kg on days 1 through 5 of every 28 days. The first dose of HCQ each day will be followed 2 hours later by 1,000 mg/m2 devimistat (for patients < 45 kg) and 2,000 mg/m2 of devimistat (for patients ≥ 45 kg) administered over 2 hours. A maximum of 36 patients will be enrolled for the phase I portion, 18 for each patient group. In the phase 2 portion of the study, only relapsed or refractory CCS patients will be enrolled, and the response rate will be determined using RECIST 1.1. In phase 2, pharmacokinetics, duration of response, clinical benefit rate, progression-free survival, overall survival, safety, and patient-reported outcomes will also be assessed. This portion of the study will utilize Simon’s admissible two-stage design with 29 patients. This study started enrolling participants in November 2021 and has dosed six patients to date. The first two dose-escalation cohorts for patients ≥45 kg have been completed without DLT and the third dose level will be opening shortly. Clinical trial information: NCT04593758.

Efficacy and safety of larotrectinib in pediatric patients with tropomyosin receptor kinase (TRK) fusion-positive cancer: An expanded dataset

10030

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are oncogenic drivers in various tumor types across all ages. Larotrectinib is a first-in-class, central nervous system (CNS)-active, highly selective tropomyosin receptor kinase (TRK) inhibitor approved for pediatric and adult patients (pts) with TRK fusion-positive cancer, demonstrating an objective response rate (ORR) of 88% across 78 pediatric pts with non-CNS cancers (van Tilburg et al, SIOP 2021). We report an analysis of the efficacy and safety of larotrectinib in an expanded dataset of pediatric pts with TRK fusion-positive cancer. Methods: Pediatric pts (< 18 years) with non-CNS TRK fusion-positive cancer in larotrectinib clinical trials (NCT02637687, NCT02576431) were included and ORR (RECIST v1.1) was investigator (INV)-assessed. Data cut-off was July 20, 2021. Results: A total of 94 pts were included in this analysis. Tumor types included infantile fibrosarcoma (52%), other soft tissue sarcoma (40%), congenital mesoblastic nephroma (2%), thyroid cancer (2%), bone sarcoma (1%), breast cancer (1%), and melanoma (1%). Pts had gene fusions involving NTRK1 (43%), NTRK2 (3%), or NTRK3 (54%). Median age was 2.2 years (range 0–18 years). Of the 62 (66%) pts who received prior systemic therapy, 32 (52%) received ≥2 lines. The INV-assessed best ORR for the 93 evaluable pts was 84% (95% confidence interval [CI] 75–91): 35 (38%) complete response (CR; including two pending confirmation and 10 pathological CR), 43 (46%) partial response (two pending confirmation), 11 (12%) stable disease, two (2%) progressive disease, and two (2%) not determined. The median time to response was 1.8 months. Overall, median duration of response was 43.3 months (95% CI 23.4–NE); median follow-up was 26.0 months. Median progression-free survival and overall survival (OS) were 37.4 months (95% CI 22–NE) and not reached, respectively; median follow-up was 21.2 and 30.3 months, respectively. The 36-month OS rate was 93% (95% CI 86–99). Treatment duration ranged from 1+ to 63+ months. At data cut-off, 31 pts had progressed; 18 continued treatment post-progression for ≥4 weeks. There were no treatment-related deaths. Treatment-related adverse events (TRAEs) occurred in 81% of pts (23% were Grade [G] 1, 28% G2, 25% G3, and 5% G4). The most common TRAE was increased aspartate aminotransferase (31 pts [33%]). Four pts (4%) discontinued treatment due to TRAEs. Neurological TRAEs occurred in 12% of pts (5% were G1, 4% G2, and 2% G3). The most common neurological TRAE was headache (5 pts [5%]). Conclusions: In this expanded dataset, larotrectinib continues to demonstrate rapid and durable tumor-agnostic efficacy, extended survival, and a favorable safety profile in pediatric pts with TRK fusion-positive cancer. These results highlight the importance of identifying NTRK gene fusions in pediatric solid tumors. Clinical trial information: NCT02576431, NCT02637687.

Atraumatic Spinal Epidural Hematoma as Initial Presentation of Hemophilia A in an Infant

ABSTRACT

Hemophilia A is characterized by deficiency of factor VIII. We present a unique, illustrative case of an infant with a short history of neck pain and irritability without neurological deficits who was found to have a spinal epidural hematoma. The subsequent investigation for the etiology, including workup for nonaccidental trauma, led to a diagnosis of severe hemophilia A.

Locoregional infusion of HER2-specific CAR T cells in children and young adults with recurrent or refractory CNS tumors: an interim analysis

Locoregional delivery of chimeric antigen receptor (CAR) T cells has resulted in objective responses in adults with glioblastoma, but the feasibility and tolerability of this approach is yet to be evaluated for pediatric central nervous system (CNS) tumors. Here we show that engineering of a medium-length CAR spacer enhances the therapeutic efficacy of human erb-b2 receptor tyrosine kinase 2 (HER2)-specific CAR T cells in an orthotopic xenograft medulloblastoma model. We translated these findings into BrainChild-01 ( NCT03500991 ), an ongoing phase 1 clinical trial at Seattle Children's evaluating repetitive locoregional dosing of these HER2-specific CAR T cells to children and young adults with recurrent/refractory CNS tumors, including diffuse midline glioma. Primary objectives are assessing feasibility, safety and tolerability; secondary objectives include assessing CAR T cell distribution and disease response. In the outpatient setting, patients receive infusions via CNS catheter into either the tumor cavity or the ventricular system. The initial three patients experienced no dose-limiting toxicity and exhibited clinical, as well as correlative laboratory, evidence of local CNS immune activation, including high concentrations of CXCL10 and CCL2 in the cerebrospinal fluid. This interim report supports the feasibility of generating HER2-specific CAR T cells for repeated dosing regimens and suggests that their repeated intra-CNS delivery might be well tolerated and activate a localized immune response in pediatric and young adult patients.

Abstract CT020: Long-term outcomes of patients with TRK fusion cancer treated with larotrectinib

Introduction: Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers in various tumor types. Larotrectinib is a first-in-class, highly selective, central nervous system (CNS)-active TRK inhibitor approved in over 40 countries, including the US, for the treatment of adult and pediatric patients with TRK fusion cancer. Larotrectinib was approved by the FDA in 2018 based on efficacy and safety outcomes in a primary analysis cohort of 55 patients with TRK fusion cancer from 3 clinical trials (Drilon A et al. NEJM. 2018). Here, we report long-term efficacy follow-up for larotrectinib and molecular data on co-occurring mutations in this primary analysis cohort. Methods: Patients with non-primary CNS TRK fusion cancer treated with larotrectinib were identified from 3 clinical trials (NCT02122913, NCT02576431, NCT02637687). NTRK gene status was determined by local molecular testing. Adult and pediatric patients received larotrectinib 100 mg and 100 mg/m2 twice daily, respectively. The primary endpoint was investigator-assessed objective response rate (ORR) (per RECIST v1.1). Next-generation sequencing was performed on pre-treatment tumor samples from a subset of patients with evaluable tumor material (n=31) using the FoundationOne® CDx assay. The data cut-off was July 15, 2019. Results: A total of 55 patients with 17 different tumor types were included in the primary analysis cohort. Median age was 45 years (range 0.3-76 years). Patients had gene fusions involving NTRK1 (45%), NTRK2 (2%), or NTRK3 (53%). For 31 patients the detailed genomic profile, including co-occurring mutations, will be presented. Forty-four (80%) patients had received prior systemic therapy, with a median of 2 prior therapies (range 0-10). ORR with larotrectinib was 80% (95% confidence interval [CI] 67-90%); 13 (24%) patients had a complete response (CR), 31 (56%) patients had a partial response (PR), 5 (9%) patients had stable disease, and 6 (11%) patients had progressive disease. With longer follow-up, best response for 4 patients improved from PR to CR. Median duration of response and progression-free survival were 35.2 months (95% CI 19.8-not estimable [NE]) and 25.8 months (95% CI 9.9-NE), respectively. Median overall survival (OS) was not reached (95% CI 44.4-NE) over a median follow-up of 32.5 months. The 36-month OS rate was 76% (95% CI 63-89%). In an expanded safety population (n=279), larotrectinib-related adverse events were mainly Grade 1-2. Conclusions: Larotrectinib demonstrated a robust response rate with long durability and extended survival benefits in adult and pediatric patients with TRK fusion cancer. These data highlight the importance of identifying NTRK gene fusions in patients with cancer.

Citation Format: Alexander Drilon, Shivaani Kummar, Catherine M. Albert, Ramamoorthy Nagasubramanian, Jaclyn F. Hechtman, John A. Reeves, Georg Beckmann, Marion Rudolph, Justyna A. Wierzbińska, Laura Dima, Nicoletta Brega, Theodore W. Laetsch, David S. Hong. Long-term outcomes of patients with TRK fusion cancer treated with larotrectinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT020.

Long-term efficacy and safety of larotrectinib in an integrated dataset of patients with TRK fusion cancer

3108

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions encode tropomyosin receptor kinase (TRK) fusion proteins, which are oncogenic drivers in various tumor types. Larotrectinib is a first-in-class, highly selective, CNS-active TRK inhibitor approved to treat adult and pediatric patients with TRK fusion cancer. Larotrectinib demonstrated an objective response rate (ORR) of 78% and a median progression-free survival (PFS) of 36.8 months in an integrated analysis of 175 patients with non-primary CNS TRK fusion cancer (McDermott et al, ESMO 2020). We report updated efficacy and safety data with longer follow-up in an expanded dataset. Methods: Data were pooled from three clinical trials of patients with non-primary CNS TRK fusion cancer treated with larotrectinib. Larotrectinib was administered until disease progression, withdrawal, or unacceptable toxicity. Response was assessed by investigators using RECIST v1.1. Data cutoff: July 20, 2020. Results: As of data cutoff, 218 patients were treated with larotrectinib, of which 206 were evaluable for efficacy. There were 21 different tumor types, the most common being soft tissue sarcoma (STS [46%], including infantile fibrosarcoma [20%] and other STS [26%]), thyroid (13%), salivary gland (11%), lung (9%), and colorectal (5%). The median age was 38.0 years (range 0.1–84.0). Patients were heavily pretreated with 45% having received 2 or more prior lines of systemic therapy; 27% had 0 prior lines of systemic therapy. The ORR was 75% (95% CI 68–81): 45 (22%) complete response, 109 (53%) partial response (PR), 33 (16%) stable disease (SD), and 13 (6%) progressive disease (PD). Nineteen patients had brain metastases at baseline, with 15 evaluable for efficacy. The ORR for patients with brain metastases was 73% (95% CI 45–92): 11 PR, 2 SD, and 2 PD. Among all evaluable patients, the median time to response was 1.8 months (range 0.9–9.1). With a median follow up of 22.3 months, the median duration of response was 49.3 months (95% CI 27.3–not estimable). Treatment duration ranged from 0.03+ to 60.4+ months. Median PFS was 35.4 months (95% CI 23.4–55.7) with a median follow up of 20.3 months. At a median follow-up of 22.3 months, median overall survival (OS) was not reached and 36-month OS was 77% (95% CI 69–84). Treatment-related adverse events (TRAEs) were mainly Grade 1–2, with 18% having Grade 3–4 TRAEs. Only 2% of patients discontinued due to TRAEs. Conclusions: These results highlight the importance of testing for NTRK gene fusions in patients with cancer because the majority of patients with TRK fusion cancer treated with larotrectinib had long-term clinical benefit. The safety profile continued to be favorable and no new safety signals were identified. Clinical trial information: NCT02576431, NCT02122913, NCT02637687.

Abstract CT199: Larotrectinib in TRK fusion cancer patients: Outcomes by prior therapy and performance status

Introduction: Larotrectinib, a highly selective Food and Drug Administration- and European Medicines Agency-approved TRK inhibitor, achieved an objective response rate (ORR) of 79% and a median duration of response (DoR) of 35.2 months across various cancers (Hong et al. Lancet Oncol. In press). In this data set, outcomes by the number of lines of prior therapy or baseline performance status have not previously been reported.

Methods: Data were pooled from three clinical trials of patients with TRK fusion cancer treated with larotrectinib (NCT02122913, NCT02576431, NCT02637687). Patients were stratified based on the number of lines of prior therapy (0, 1, 2, or ≥3) and baseline Eastern Cooperative Oncology Group (ECOG) performance status (0, 1, 2, or 3). A post hoc analysis of ORR, assessed by investigators using Response Evaluation Criteria in Solid Tumors 1.1, DoR, progression-free survival (PFS), and overall survival (OS) was performed (data cut-off was February 19, 2019).

Results: A total of 159 patients were enrolled. Stratified efficacy outcomes are shown in the table. The incidence of Grade 3/4 adverse events was similar across lines of therapy.

Number of prior lines of therapy012≥3Total(n=35)(n=48)(n=34)(n=42)(N=159)ORR, % (95% CI)91 (76, 98)70 (54, 82)73 (54, 87)85 (70, 94)79 (72, 85)DoRNENENE35.235.2(19.8, NE)(15.0, NE)(7.6, NE)(22.8, NE)(22.8, NE)1.9+, 37.1+1.6+, 40.2+1.9+, 44.2+1.9+, 38.2+1.6+, 44.2+PFS25.8NENE28.328.3(15.2, NE)(9.9, NE)(7.0, NE)(16.6, NE)(22.1, NE)0.03+, 38.8+0.03+, 42.1+0.03+, 45.2+0.03+, 40.0+0.03+, 45.2+OSNENE36.544.444.4(NE, NE)(33.4, NE)(36.5, NE)(NE, NE)(36.5, NE)0.03+, 39.9+0.5+, 43.1+0.3+, 47.2+1.0+, 44.40.03+, 47.2+ECOG performance status0123Total(n=76)(n=61)(n=19)(n=3)(N=159)ORR, % (95% CI)91 (81, 96)69 (56, 81)71 (44, 90)33 (1, 91)79 (72, 85)DoR35.226.3NENE35.2(22.8, NE)(19.8, NE)(7.2, NE)(22.8, NE)1.8+, 40.2+1.6+, 44.2+1.9+, 29.5+1.6+, 44.2+PFS36.825.8NENE28.3(24.6, NE)(9.0, NE)(2.7, NE)(1.1, NE)(22.1, NE)0.03+, 42.1+0.03+, 45.2+0.03+, 30.4+0.03+, 1.7+0.03+, 45.2+All data values show median (95% CI) and range in months, unless otherwise stated. CI, confidence interval; DoR, duration of response; ECOG, Eastern Cooperative Oncology Group; NE, not estimable; ORR, objective response rate; OS, overall survival; PFS, progression-free survival.

Conclusion: While response rates were highest in patients who were treatment-naïve or with an ECOG performance status of 0, larotrectinib benefited patients across varying degrees of pre-treatment or performance status.

Citation Format: Alexander Drilon, Cornelis M. van Tilburg, Anna F. Farago, Shivaani Kummar, Jordan Berlin, Catherine M. Albert, Ray McDermott, Ulrik N. Lassen, John A. Reeves, Nicoletta Brega, Barrett H. Childs, Theodore W. Laetsch, David S. Hong. Larotrectinib in TRK fusion cancer patients: Outcomes by prior therapy and performance status [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 CT199.

Abstract B67: EGFR as a target in pediatric solid tumors

The epidermal growth factor receptor (EGFR or HER1) is a cell surface tyrosine kinase receptor that is expressed in a diverse group of epithelial and nonepithelial tissues and broadly associated with cell proliferation and differentiation. Expression of wild-type EGFR and activating mutations are described in many malignancies, including a variety of pediatric solid tumors. In the setting of malignancy, EGFR has been associated with aggressive disease, chemotherapy resistance, and increased metastatic potential. Employment of anti-EGFR agents has yielded some promising results, but they are not always effective against all cancer-associated aberrant EGFR expression and are frequently associated with notable off-tumor toxicities due to the expression of EGFR in normal tissue. The unique EGFR monoclonal antibody (mAb) 806 selectively binds to an epitope on the extracellular portion of human EGFR expressed on the surface of tumor cells. This antibody recognizes the deletion mutant EGFRvIII commonly present in glioblastomas and some other solid tumors as well as wild-type EGFR. We designed a phase I trial for pediatric and young adult patients with recurrent or refractory solid tumors expressing epidermal growth factor (EGFR) to examine the safety and feasibility of administering autologous, peripheral blood-derived T cells that have been genetically modified to express a second-generation (2G) EGFR806-specific chimeric antigen receptor (CAR). Literature review and evaluation of EGFR immunohistochemistry (IHC) performed on several tissue microarrays were used to estimate the percentage of EGFR positivity among common subtypes of pediatric cancer. Using these tools, we hypothesized that 15-40% of otherwise eligible patients would meet the eligibility criteria of EGFR positivity. The trial opened in August of 2018. To date, a total of 33 patient tumors have undergone EGFR IHC to determine eligibility for the trial. 9/33 (27.3%) have been EGFR+. EGFR+ histologies include BCOR fusion sarcoma (3), germ cell tumor (2), osteosarcoma, Ewing sarcoma, desmoplastic small round cell tumor, and synovial sarcoma. Our eligibility testing thus far demonstrates EGFR expression by IHC in a variety of histologies. Two rare diseases, recurrent BCOR fusion sarcoma and refractory germ cell tumors, have demonstrated a significantly higher rate of EGFR IHC positivity, (3/3)100% and (2/3) 66.7%, respectively. These early results indicate that this trial and other anti-EGFR therapies may be most effectively targeted to certain subgroups of pediatric cancer patients.

Citation Format: Catherine M. Albert, Navin R. Pinto, Erin R. Rudzinski, Julie R. Park. EGFR as a target in pediatric solid tumors [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B67.

Activating variants in PDGFRB result in a spectrum of disorders responsive to imatinib monotherapy

More than 50 individuals with activating variants in the receptor tyrosine kinase PDGFRB have been reported, separated based on clinical features into solitary myofibromas, infantile myofibromatosis, Penttinen syndrome with premature aging and osteopenia, Kosaki overgrowth syndrome, and fusiform aneurysms. Despite their descriptions as distinct clinical entities, review of previous reports demonstrates substantial phenotypic overlap. We present a case series of 12 patients with activating variants in PDGFRB and review of the literature. We describe five patients with PDGFRB activating variants whose clinical features overlap multiple diagnostic entities. Seven additional patients from a large family had variable expressivity and late-onset disease, including adult onset features and two individuals with sudden death. Three patients were treated with imatinib and had robust and rapid response, including the first two reported infants with multicentric myofibromas treated with imatinib monotherapy and one with a recurrent p.Val665Ala (Penttinen) variant. Along with previously reported individuals, our cohort suggests infants and young children had few abnormal features, while older individuals had multiple additional features, several of which appeared to worsen with advancing age. Our analysis supports a diagnostic entity of a spectrum disorders due to activating variants in PDGFRB. Differences in reported phenotypes can be dramatic and correlate with advancing age, genotype, and to mosaicism in some individuals.

Quality of life of adults and children with TRK fusion cancer treated with larotrectinib compared to the general population

3614

Background: NTRK gene fusions occur in diverse tumor types in adults and children. The selective TRK inhibitor, larotrectinib, has shown high response rates, durable disease control, and a favorable safety profile in patients (pts) with TRK fusion cancer. We report an expanded quality of life (QoL) analysis for pts treated with larotrectinib. Methods: QoL data were collected in two trials of larotrectinib in pts with TRK fusion cancer using EORTC QLQ-C30 (adults) and PedsQL (children) questionnaires, and were analyzed descriptively and longitudinally. EORTC QLQ-C30 global health scores (GHS) and PedsQL total scores range from 0 to 100, with higher scores indicating better QoL. We calculated the proportion of pts with normal/above and below normal QoL scores compared to values in the literature for the US general population. Results: By July 2019, 126 pts with TRK fusion cancer (74 adults, 24 children ≥2 yrs, and 28 infants <2 yrs) had received larotrectinib and completed baseline (BL) and ≥1 post-BL questionnaire. Most pts had clinically meaningful QoL improvements that reached or exceeded the minimally important difference (Table); a positive change from BL was also seen in infants: mean best change of 12.0 (SD 13.8). Of 52 adults with BL EORTC QLQ-C30 GHS at or above the population norm, 51 remained in this category on treatment and 1 moved into the below normal category. Of 22 adults with BL scores below the population norm, 20 moved into the normal/above normal category. All 9 children aged ≥2 yrs with BL PedsQL scores at or above the population norm remained in this category on treatment. Of 15 children with BL scores below the population norm, 10 moved into the normal/above normal category. Sustained QoL improvements (change from BL ≥0) occurred by 2 months of treatment in 69% of adults and 75% of children. Median duration of sustained improvement in EORTC QLQ-C30 GHS and PedsQL total score was 12.0 months (range 1.7–20.3) and not estimable (range 1.1–23.0), respectively. Conclusions: Adults and children with TRK fusion cancer treated with larotrectinib had rapid, clinically meaningful, and sustained improvements in QoL. Clinical trial information: NCT02576431, NCT02637687 . [Table: see text]

Larotrectinib in patients with TRK fusion-positive solid tumours: a pooled analysis of three phase 1/2 clinical trials

BACKGROUND

The selective TRK inhibitor larotrectinib was approved for paediatric and adult patients with advanced TRK fusion-positive solid tumours based on a primary analysis set of 55 patients. The aim of our analysis was to explore the efficacy and long-term safety of larotrectinib in a larger population of patients with TRK fusion-positive solid tumours.

METHODS

Patients were enrolled and treated in a phase 1 adult, a phase 1/2 paediatric, or a phase 2 adolescent and adult trial. Some eligibility criteria differed between these studies. For this pooled analysis, eligible patients were aged 1 month or older, with a locally advanced or metastatic non-CNS primary, TRK fusion-positive solid tumour, who had received standard therapy previously if available. This analysis set includes the 55 patients on which approval of larotrectinib was based. Larotrectinib was administered orally (capsule or liquid formulation), on a continuous 28-day schedule, to adults mostly at a dose of 100 mg twice daily, and to paediatric patients mostly at a dose of 100 mg/m² (maximum of 100 mg) twice daily. The primary endpoint was objective response as assessed by local investigators in an intention-to-treat analysis. Contributing trials are registered with ClinicalTrials.gov, NCT02122913 (active not recruiting), NCT02637687 (recruiting), and NCT02576431 (recruiting).

FINDINGS

Between May 1, 2014, and Feb 19, 2019, 159 patients with TRK fusion-positive cancer were enrolled and treated with larotrectinib. Ages ranged from less than 1 month to 84 years. The proportion of patients with an objective response according to investigator assessment was 121 (79%, 95% CI 72-85) of 153 evaluable patients, with 24 (16%) having complete responses. In a safety population of 260 patients treated regardless of TRK fusion status, the most common grade 3 or 4 larotrectinib-related adverse events were increased alanine aminotransferase (eight [3%] of 260 patients), anaemia (six, 2%), and decreased neutrophil count (five [2%]). The most common larotrectinib-related serious adverse events were increased alanine aminotransferase (two [<1%] of 260 patients), increased aspartate aminotransferase (two [<1%]), and nausea (two [<1%]). No treatment-related deaths occurred.

INTERPRETATION

These data confirm that TRK fusions define a unique molecular subgroup of advanced solid tumours for which larotrectinib is highly active. Safety data indicate that long-term administration of larotrectinib is feasible.

FUNDING

Bayer and Loxo Oncology.

TRK Fusion Cancers in Children: A Clinical Review and Recommendations for Screening

Chromosomal translocations involving the NTRK1, NTRK2, and NTRK3 genes (TRK fusions), which encode the neurotrophin tyrosine kinase receptors TRKA, TRKB, and TRKC, can result in constitutive activation and aberrant expression of TRK kinase. Certain cancers almost universally harbor TRK fusions, including infantile fibrosarcoma, cellular congenital mesoblastic nephroma, secretory breast cancer, and mammary analog secretory carcinoma of the salivary gland. TRK fusions have also been identified at lower frequencies across a broad range of other pediatric cancers, including undifferentiated sarcomas, gliomas, papillary thyroid cancers, spitzoid neoplasms, inflammatory myofibroblastic tumors, and acute leukemias. Here we review the prevalence and diseases associated with TRK fusions and methods of detection of these fusions in light of the recent development of selective TRK inhibitors, such as larotrectinib, which demonstrated a 75% response rate across children and adults with TRK fusion cancers. We provide recommendations for screening pediatric tumors for the presence of TRK fusions, including the use of immunohistochemistry or fluorescence in situ hybridization for patients with tumors likely to harbor TRK fusions. Further, we recommend next-generation sequencing for tumors that have a relatively low prevalence of TRK fusions, both to identify patients who may benefit from TRK inhibition and to identify other targetable oncogenic drivers that exist in the same tumor types.

The use of neoadjuvant larotrectinib in the management of children with locally advanced TRK fusion sarcomas

Background

The highly selective oral tropomyosin receptor kinase (TRK) inhibitor larotrectinib has demonstrated significant activity in adult and pediatric TRK fusion cancers. In the current study, the authors describe the clinical course of children with locally advanced TRK fusion sarcoma who were treated preoperatively with larotrectinib and underwent subsequent surgical resection.

Methods

A total of 24 children were treated on a pediatric phase 1 trial of larotrectinib (ClinicalTrials.gov identifier NCT02637687). Five children who had a documented TRK fusion sarcoma and underwent surgical resection were included in the current analysis. Tumor response (Response Evaluation Criteria In Solid Tumors [RECIST] version 1.1) and surgical outcomes were collected prospectively.

Results

A total of 5 patients (median age, 2 years; range, 0.4‐12 years) had locally advanced infantile fibrosarcoma (3 patients) or soft‐tissue sarcoma (2 patients). Four patients had disease that was refractory to standard therapy. All 5 patients achieved a partial response to larotrectinib by version 1.1 of RECIST and underwent surgical resection after a median of 6 cycles (range, 4‐9 cycles) of treatment. Surgical resections were R0 (negative resection margins with no tumor at the inked resection margin) in 3 patients, R1 (microscopic residual tumor at the resection margin) in 1 patient, and R2 (macroscopic residual tumor at the resection margin) in 1 patient. Three patients achieved complete (2 patients) or near‐complete (>98% treatment effect; 1 patient) pathologic responses. These patients remained in follow‐up and were no longer receiving larotrectinib for a minimum of 7 to 15 months postoperatively. Two patients had viable tumor at the time of surgical resection and positive resection margins and continued to receive adjuvant larotrectinib. No patients experienced postoperative complications or wound healing issues.

Conclusions

Children with locally advanced TRK fusion sarcomas may proceed to surgical resection after treatment with the selective TRK inhibitor larotrectinib, thereby sparing them the potentially significant morbidity noted with current approaches. These results support the evaluation of larotrectinib as presurgical therapy in children with newly diagnosed TRK fusion sarcomas.

Children with locally advanced tropomyosin receptor kinase (TRK) fusion sarcomas may proceed to surgical resection after neoadjuvant treatment with the selective oral TRK inhibitor larotrectinib, sparing them the potentially significant morbidity noted with current approaches. The results of the current study support the further evaluation of larotrectinib as neoadjuvant therapy in children with newly diagnosed TRK fusion sarcomas.

Larotrectinib for paediatric solid tumours harbouring NTRK gene fusions: phase 1 results from a multicentre, open-label, phase 1/2 study

BACKGROUND

Gene fusions involving NTRK1, NTRK2, or NTRK3 (TRK fusions) are found in a broad range of paediatric and adult malignancies. Larotrectinib, a highly selective small-molecule inhibitor of the TRK kinases, had shown activity in preclinical models and in adults with tumours harbouring TRK fusions. This study aimed to assess the safety of larotrectinib in paediatric patients.

METHODS

This multicentre, open-label, phase 1/2 study was done at eight sites in the USA and enrolled infants, children, and adolescents aged 1 month to 21 years with locally advanced or metastatic solid tumours or CNS tumours that had relapsed, progressed, or were non-responsive to available therapies regardless of TRK fusion status; had a Karnofsky (≥16 years of age) or Lansky (<16 years of age) performance status score of 50 or more, adequate organ function, and full recovery from the acute toxic effects of all previous anticancer therapy. Following a protocol amendment on Sept 12, 2016, patients with locally advanced infantile fibrosarcoma who would require disfiguring surgery to achieve a complete surgical resection were also eligible. Patients were enrolled to three dose cohorts according to a rolling six design. Larotrectinib was administered orally (capsule or liquid formulation), twice daily, on a continuous 28-day schedule, in increasing doses adjusted for age and bodyweight. The primary endpoint of the phase 1 dose escalation component was the safety of larotrectinib, including dose-limiting toxicity. All patients who received at least one dose of larotrectinib were included in the safety analyses. Reported here are results of the phase 1 dose escalation cohort. Phase 1 follow-up and phase 2 are ongoing. This trial is registered with ClinicalTrials.gov, number NCT02637687.

FINDINGS

Between Dec 21, 2015, and April 13, 2017, 24 patients (n=17 with tumours harbouring TRK fusions, n=7 without a documented TRK fusion) with a median age of 4·5 years (IQR 1·3-13·3) were enrolled to three dose cohorts: cohorts 1 and 2 were assigned doses on the basis of both age and bodyweight predicted by use of SimCyp modelling to achieve an area under the curve equivalent to the adult doses of 100 mg twice daily (cohort 1) and 150 mg twice daily (cohort 2); and cohort 3 was assigned to receive a dose of 100 mg/m² twice daily (maximum 100 mg per dose), regardless of age, equating to a maximum of 173% of the recommended adult phase 2 dose. Among enrolled patients harbouring TRK fusion-positive cancers, eight (47%) had infantile fibrosarcoma, seven (41%) had other soft tissue sarcomas, and two (12%) had papillary thyroid cancer. Adverse events were predominantly grade 1 or 2 (occurring in 21 [88%] of 24 patients); the most common larotrectinib-related adverse events of all grades were increased alanine and aspartate aminotransferase (ten [42%] of 24 each), leucopenia (five [21%] of 24), decreased neutrophil count (five [21%] of 24), and vomiting (five [21%] of 24). Grade 3 alanine aminotransferase elevation was the only dose-limiting toxicity and occurred in one patient without a TRK fusion and with progressive disease. No grade 4 or 5 treatment-related adverse events were observed. Two larotrectinib-related serious adverse events were observed: grade 3 nausea and grade 3 ejection fraction decrease during the 28-day follow-up after discontinuing larotrectinib and while on anthracyclines. The maximum tolerated dose was not reached, and 100 mg/m² (maximum of 100 mg per dose) was established as the recommended phase 2 dose. 14 (93%) of 15 patients with TRK fusion-positive cancers achieved an objective response as per Response Evaluation Criteria In Solid Tumors version 1.1; the remaining patient had tumour regression that did not meet the criteria for objective response. None of the seven patients with TRK fusion-negative cancers had an objective response.

INTERPRETATION

The TRK inhibitor larotrectinib was well tolerated in paediatric patients and showed encouraging antitumour activity in all patients with TRK fusion-positive tumours. The recommended phase 2 dose was defined as 100mg/m² (maximum 100 mg per dose) for infants, children, and adolescents, regardless of age.

FUNDING

Loxo Oncology Inc.

Infantile NTRK-associated Mesenchymal Tumors

Pediatric fibroblastic/myofibroblastic lesions are a relatively common group of tumors with varying morphologies, for which the molecular mechanisms are becoming increasingly well characterized. Congenital infantile fibrosarcoma (CIFS), perhaps the most well studied of these lesions is characterized by a recurrent ETV6-NTRK3 gene fusion. However, a notable subset of locally aggressive congenital/infantile soft tissue lesions with similar morphologic features to CIFS, have not to-date, shown evidence of any canonical molecular aberration. We describe 6 patients with mesenchymal tumors composed of infiltrative fibroblastic/myofibroblastic tumor cells and showing a morphologic spectrum of features much analogous to that previously described in CIFS but without ETV6 fusion transcripts. These tumors lacked a uniform immunoprofile, but showed variable expression of CD34, S100, smooth muscle actin, and CD30. All patients first developed a mass in infancy (≤2 months of age). Using next-generation DNA sequencing, TMP3-NTRK1 fusions were identified in 4 cases, an LMNA-NTRK1 fusion in one case, and a variant EML4-NTRK3 fusion in one case. Similar to infantile fibrosarcoma, these tumors were locally aggressive (with local recurrences if incompletely excised) and rarely metastasized (lung metastases in one patient). Proper identification of these tumors including investigation for NTRK family gene rearrangements is essential for diagnostic accuracy, as well as for clinical management decisions. Given the morbidity associated with radical resection of large soft tissue tumors, children with unresectable, recurrent, and/or metastatic disease may benefit from treatment with NTRK targeted therapies.

Inhibition of porcupine prolongs metastasis free survival in a mouse xenograft model of Ewing sarcoma

The most pressing unmet clinical need for patients with Ewing sarcoma (ES) is the prevention and treatment of metastasis. The Wnt signaling pathway regulates a number of cellular functions associated with metastasis, including proliferation, motility, and stem cell self-renewal. Functional interaction between Wnt ligands and their receptors requires palmitoylation by Porcupine (Porcn), making this an ideal therapeutic target. We studied the effect of WNT974, a potent, selective Porcn inhibitor, on ES metastasis. In vitro, WNT974 does not affect ES proliferation or sarcosphere formation, but suppresses multiple transcriptional regulators of metastasis and inhibits cell migration. In vivo, in an orthotopic implantation/amputation model of spontaneous distant metastasis, single agent WNT974 treatment leads to a significant delay in formation of lung metastasis and a substantial improvement in post-amputation survival without a major effect on primary tumor growth. The drug produces no survival benefit in a tail vein injection model, supporting the hypothesis that WNT974 inhibits early steps in the metastatic cascade, such as migration and invasion. Our findings strongly implicate Wnt signaling in the early steps of ES metastasis and demonstrate that WNT974 has the potential to significantly improve the survival of ES patients through the specific inhibition of metastasis.

Abstract 4119: Inhibition of PORCN prolongs metastasis free survival in a mouse model of Ewing sarcoma

Metastatic disease is the most important factor in determining the survival of patients with Ewing sarcoma (ES). Although intensive cytotoxic chemotherapy has improved the survival of patients with localized disease, the survival rate for patients with metastatic disease remains dismal, and the most pressing unmet need in ES is to prevent and treat metastasis better. The Wnt signaling pathway is a key regulator of a number of cellular functions associated with metastasis, including proliferation, motility, and stem cell self-renewal. A single enzyme, Porcupine (Porcn), mediates post-translational palmitoylation of Wnt ligands, and it's activity is required for secretion of all 17 Wnt ligands, making it an attractive target for a pan-Wnt inhibitor. We have studied the effect of LGK974, a potent, selective, Porcn inhibitor, on Ewing sarcoma metastasis. In vitro, we have observed that LGK974 does not affect proliferation or sarcosphere formation, but inhibits migration of ES cell lines through the suppression of expression of multiple transcriptional regulators of Epithelial-Mesenchymal Transition (EMT). In our orthotopic implantation/amputation mouse model, single agent LGK974 treatment leads to significant delay in formation of lung metastasis following amputation of the affected leg, without a significant effect on primary tumor growth. This delay leads to a significant post-amputation survival benefit in multiple xenografts. In LGK974 treated xenografts, the expression of multiple EMT related transcription factors were observed to be suppressed. Furthermore, in tail vein injection models, LGK974 did not produce a survival benefit, suggesting that LGK974 effects Ewing sarcoma metastasis by inhibiting early steps in the metastatic cascade, such as migration and invasion. Our findings strongly implicate Wnt signaling in the early steps of ES metastasis and demonstrate that LGK974 has the potential to significantly improve the survival of ES patients through the specific inhibition of metastasis.

Citation Format: Masanori Hayashi, Alissa C. Baker, Seth D. Goldstein, Catherine M. Albert, Kyle W. Jackson, David M. Loeb. Inhibition of PORCN prolongs metastasis free survival in a mouse model of Ewing sarcoma. [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 4119.

Highly personalized detection of minimal Ewing sarcoma disease burden from plasma tumor DNA

BACKGROUND

Even though virtually all patients with Ewing sarcoma achieve a radiographic complete response, up to 30% of patients who present with localized disease and up to 90% of those who present with metastases experience a metastatic disease recurrence, highlighting the inability to identify patients with residual disease at the end of therapy. Up to 95% of Ewing sarcomas carry a driving EWS-ETS translocation that has an intronic breakpoint that is specific to each tumor, and the authors developed a system to quantitatively detect the specific breakpoint DNA fragment in patient plasma.

METHODS

The authors used a long-range multiplex polymerase chain reaction (PCR) technique to identify tumor-specific EWS-ETS breakpoints in Ewing sarcoma cell lines, patient-derived xenografts, and patient tumors, and this sequence was used to design tumor-specific primer sets to detect plasma tumor DNA (ptDNA) by droplet digital PCR in xenograft-bearing mice and patients.

RESULTS

Tumor-specific breakpoint DNA fragments were detected in the plasma of xenograft-bearing mice, and the signal correlated with tumor burden during primary tumor growth, after surgical resection, and at the time of metastatic disease recurrence. Furthermore, the authors were able to detect the specific breakpoint in plasma DNA obtained from 3 patients with Ewing sarcoma and in 2 patients the authors were able to detect ptDNA when there was radiographically undetectable disease present.

CONCLUSIONS

The use of droplet digital PCR to detect tumor-specific EWS-ETS fusion gene breakpoint ptDNA fragments can be developed into a highly personalized biomarker of disease recurrence that can be optimized in animal studies for ultimate use in patients. Cancer 2016;122:3015-3023. © 2016 American Cancer Society.

Abstract B37: Detection of sarcoma circulating tumor cells using a size based microfiltration device

The inability to effectively treat hematogenous metastasis remains the largest challenge of sarcoma therapy. The ability to isolate, quantify, and study circulating tumor cells (CTC) in sarcomas has the potential to enhance our understanding of the biology of metastasis, altering the way we treat patients with high grade sarcomas. Using a size based filtration device, CellSieve™, we were able to successfully identify and quantify CTC in a metastatic xenograft model as well as in blood samples from patients with high grade sarcomas. In mice, we utilized our orthotopic implantation/amputation model of metastasis. Using a TdTomato-expressing Ewing sarcoma cell line and a cocktail of fluorescently labeled antibodies to vimentin and CD45, we were able to detect both CTC and circulating tumor clusters (CTCL) in mice with growing tumors and with metastatic disease, but not in mice immediately post-amputation. These experiments were augmented with samples collected from patients with high grade sarcomas. In 18 samples from 15 patients, we were able to identify both CTC and CTCL. Furthermore, we were also able to validate the presence of CTC by PCR amplification of sarcoma-associated chromosomal translocations. Future work will use this system to explore the biology of sarcoma metastasis by studying genetic, transcriptional, and epigenetic characteristics of CTC and CTCL and comparing these cells to those in the bulk primary tumor. We will also further explore the possibility that CTC and/or CTCL might serve as a biomarker of disease burden, response to treatment, or metastatic risk.

Citation Format: Masanori Hayashi, Peixuan Zhu, Catherine M. Albert, Diana Steppan, Gregory McCarty, Kyle W. Jackson, Cha-Mei Tang, David M. Loeb. Detection of sarcoma circulating tumor cells using a size based microfiltration device. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B37.

Abstract 3231: An orthotopic xenograft model of sarcoma metastasis demonstrates essential role of tumor microenvironment for metastasis

Sarcoma metastasis is a multi-step process that includes migration, intravasation into the circulation, extravasation and invasion to distant tissue, and distant tumor growth, and because commonly used xenograft models do not account for every step in the process, we sought to develop a novel metastasis model system. Our technique involves implanting small fragments of patient-derived xenografts into either the tibia or gastrocnemius muscle of NOD/SCID/IL-2Rγ knock-out mice and amputating the affected limb when the tumor reaches at least 1 cm in diameter. Mice are then followed for the development of distant metastases. We found that Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma xenografts all undergo distant metastasis when implanted in an orthotopic location, but do not metastasize after subcutaneous implantation, even when the subcutaneous tumor is excised and mice are observed long-term post-excision. We also investigated whether the difference in metastatic potential is related to cell intrinsic or cell extrinsic factors. Analysis by immunofluorescence revealed that tumors are infiltrated by macrophages regardless of site of implantation, but that the polarization of these macrophages differs. We also found differences in expression of arginase and NOS2 based on site of xenograft implantation. Thus, we have demonstrated that sarcoma patient-derived xenografts undergo spontaneous distant metastasis when implanted in an orthotopic location, but not when implanted in a heterotopic location, highlighting the essential role of the tumor microenvironment in determining metastatic potential. This model has significant benefits compared with the more commonly used tail vein injection model of metastasis, which bypasses the requirements for local invasion and vascular intravasation, processes that are amenable to study using our model. We have begun to use this model to investigate the mechanisms by which tumor microenvironment influences metastasis, and also are using this model for preclinical drug evaluation to determine a therapy's effect not only on growth of the primary tumor, but also on development of metastasis.

Citation Format: Seth D. Goldstein, Masanori Hayashi, Catherine M. Albert, Kyle W. Jackson, David M. Loeb. An orthotopic xenograft model of sarcoma metastasis demonstrates essential role of tumor microenvironment for metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3231. doi:10.1158/1538-7445.AM2015-3231

IGF1R- and ROR1-Specific CAR T Cells as a Potential Therapy for High Risk Sarcomas

Patients with metastatic or recurrent and refractory sarcomas have a dismal prognosis. Therefore, new targeted therapies are urgently needed. This study was designed to evaluate chimeric antigen receptor (CAR) T cells targeting the type I insulin-like growth factor receptor (IGF1R) or tyrosine kinase-like orphan receptor 1 (ROR1) molecules for their therapeutic potential against sarcomas. Here, we report that IGF1R (15/15) and ROR1 (11/15) were highly expressed in sarcoma cell lines including Ewing sarcoma, osteosarcoma, alveolar or embryonal rhabdomyosarcoma, and fibrosarcoma. IGF1R and ROR1 CAR T cells derived from eight healthy donors using the Sleeping Beauty (SB) transposon system were cytotoxic against sarcoma cells and produced high levels of IFN-γ, TNF-α and IL-13 in an antigen-specific manner. IGF1R and ROR1 CAR T cells generated from three sarcoma patients released significant amounts of IFN-γ in response to sarcoma stimulation. The adoptive transfer of IGF1R and ROR1 CAR T cells derived from a sarcoma patient significantly reduced tumor growth in pre-established, systemically disseminated and localized osteosarcoma xenograft models in NSG mice. Infusion of IGF1R and ROR1 CAR T cells also prolonged animal survival in a localized sarcoma model using NOD/scid mice. Our data indicate that both IGF1R and ROR1 can be effectively targeted by SB modified CAR T cells and that such CAR T cells may be useful in the treatment of high risk sarcoma patients.

Abstract A66: NF-kappa B is a potential therapeutic target in a subset of rhabdomyosarcomas

Rhabdomyosarcoma (RMS) is a tumor that arises from skeletal muscle progenitor cells and is the most common soft tissue sarcoma of childhood. RMS cells are characterized by impaired myogenesis and do not undergo terminal differentiation. Nuclear factor-kappa B (NF-κB) is a family of transcription factors found in virtually all mammalian cells that is commonly associated with inflammation and has been implicated in numerous malignancies. NF-κB p65 containing dimers are the most prevalent active species of NF-κB. Increased NF-κB activity has been shown to disrupt myogenesis by suppressing the differentiation of myoblasts through a regulatory circuit involving microRNA miR-29. However, the role of NF-κB in RMS is largely unexplored. The purpose of this study is to investigate the role of NF-κB in RMS tumorigenesis and evaluate its potential as a therapeutic target in this disease.

NF-κB activity was surveyed in a panel of embryonal RMS (ERMS) and alveolar RMS (ARMS) cell lines. Four out of 8 RMS cell lines (2 ERMS and 2 ARMS) demonstrated increased NF-κB activation at baseline as assessed by increased levels of p65 and phosphorylated p65 on western blotting, nuclear localization of p65 on EMSA super shift, and increased NF-κB transcriptional activity on a luciferase reporter assay. RMS cell lines, including TTC442 (ERMS), also demonstrated dose-dependent cytotoxicity after treatment with Bortezomib, a proteasome inhibitor. BAY 16-1942, a specific inhibitor of IκB kinase-β (IKK-β), was ineffective as a single agent; however, doxorubicin-induced cytotoxicity was enhanced by up to 39% in TTC442 cells treated concurrently with this agent. RH30 (ARMS), TTC442 (ERMS), and RD (ERMS) cells were transfected with IκB-SR, a doxycycline-inducible super-repressor form of IκBα, and effects on proliferation and clonogenic activity were assessed. WST-1 assay of cellular proliferation revealed growth impairment of TTC442 cells expressing the IκB-SR mutant, with average values of only 63% and 60% of control cells after 72 and 96 hours in culture. In addition, TTC442 and RH30 cells expressing the IκB-SR mutant formed 35% and 29% fewer colonies, respectively, compared to control cells when plated in low concentration. No differences in proliferation or clonogenic capacity were observed in RD cells, a line that did not show consistent NF-κB activation in our initial survey.

These data indicate that NF-κB is activated in a subset of RMS cells and suggest that modulation of NF-κB activity may affect baseline tumor growth, sensitivity to chemotherapy, and clonogenic potential of these cells. These findings support the hypothesis that NF-κB is a promising new therapeutic target for RMS.

Citation Format: Catherine M. Albert, David M. Loeb, Ido Paz-Priel. NF-kappa B is a potential therapeutic target in a subset of rhabdomyosarcomas. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A66.

Female sex as an independent risk factor for stroke in atrial fibrillation: possible mechanisms

Atrial fibrillation (AF) is an independent risk factor for thromboembolism and stroke. Women with AF are at a higher overall risk for thromboembolic stroke when compared to men with AF. Recent evidence suggests that female sex, after adjusting for stroke risk profile and sex differences in utilisation of anticoagulation, is an independent stroke risk factor in AF. The inclusion of female sex has improved the accuracy of the CHADS2 stroke risk stratification schema (Congestive heart failure, Hypertension, Age 75 years or greater, Diabetes mellitus, and prior Stroke or TIA). The newly revised and validated schema, CHA2DS2-VASc, dichotomises age and incorporates female sex and vascular disease history. The pathophysiological mechanisms to explain this increased risk in women are not well understood. According to Virchow's triad, thrombosis that leads to stroke in AF should arise from three co-existing phenomena: structural abnormalities, blood stasis, and a hypercoagulable state. Herein, we explore the sex differences in the biological processes that lead to thrombus formation as applied to Virchow's Triad. The objective of this review is to describe the potential mechanisms behind the increased risk of stroke in AF associated with female sex.

Epidemiology of atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia in the general population. Unfortunately, current treatment strategies aiming at the elimination of atrial fibrillation have limited long term success rates and significant risks. In this context, recent publications have provided many insights on potentially treatable risk factors for the occurrence of atrial fibrillation, such as alcohol, blood pressure, obesity, inflammation and nutritional factors. In this review, we summarise the current evidence on these risk factors and indicate areas in need of further investigation. The current evidence shows that blood pressure, hypertension and obesity seem to play a key role in the pathogenesis of atrial fibrillation. Preliminary evidence also suggests that inflammation is an important mediator of these associations. Knowledge of these interrelationships may eventually help to develop new treatment strategies and decrease the burden of atrial fibrillation in the general population.

Lead noise with an active-fixation defibrillation lead

Inappropriate detection and therapy is the most common adverse effect of implantable cardioverter defibrillator therapy. One mechanism is lead artifact, which usually presents late and is due to stress and fatigue of the lead components. Our experience with a defibrillator lead (Endotak Endurance EZ leads, Models 0154/0155/0156) and its method of active fixation is described. Of 20 implants with this lead, four patients were found to have noise that resulted in inappropriate detections in three. No patient received therapy as a consequence of these detections. The artifact appeared soon after implant and resolved in three of four cases by 4 weeks. None of the 16 remaining patients developed noise after this time. This is a unique lead problem that resolves with time, but it may result in inappropriate therapies and difficult management decisions in high risk patients with ventricular arrhythmias.

Triggering of sudden death from cardiac causes by vigorous exertion

BACKGROUND

Retrospective and cross-sectional data suggest that vigorous exertion can trigger cardiac arrest or sudden death and that habitual exercise may diminish this risk. However, the role of physical activity in precipitating or preventing sudden death has not been assessed prospectively in a large number of subjects.

METHODS

We used a prospective, nested case-crossover design within the Physicians' Health Study to compare the risk of sudden death during and up to 30 minutes after an episode of vigorous exertion with that during periods of lighter exertion or none. We then evaluated whether habitual vigorous exercise modified the risk of sudden death that was associated with vigorous exertion. In addition, the relation of vigorous exercise to the overall risk of sudden death and nonsudden death from coronary heart disease was assessed.

RESULTS

During 12 years of follow-up, 122 sudden deaths were confirmed among the 21,481 male physicians who were initially free of self-reported cardiovascular disease and who provided information on their habitual level of exercise at base line. The relative risk of-sudden death during and up to 30 minutes after vigorous exertion was 16.9 (95 percent confidence interval, 10.5 to 27.0; P<0.001). However, the absolute risk of sudden death during any particular episode of vigorous exertion was extremely low (1 sudden death per 1.51 million episodes of exertion). Habitual vigorous exercise attenuated the relative risk of sudden death that was associated with an episode of vigorous exertion (P value for trend=0.006). The base-line level of exercise was not associated with the overall risk of subsequent sudden death.

CONCLUSIONS

These prospective data from a study of U.S. male physicians suggest that habitual vigorous exercise diminishes the risk of sudden death during vigorous exertion.

Moderate alcohol consumption and the risk of sudden cardiac death among US male physicians

BACKGROUND

Individuals who consume high amounts of alcohol (>5 drinks/d) have increased risks of ventricular arrhythmia and sudden cardiac death (SCD). However, the relationship is less clear for drinkers of light-to-moderate amounts.

METHODS AND RESULTS

We prospectively assessed whether light-to-moderate alcohol drinkers have a decreased risk of SCD among 21 537 male participants in the Physicians Health Study who were free of self-reported cardiovascular disease and provided complete information on alcohol intake at study entry. Over 12 years of follow-up, 141 SCDs were confirmed. After control for multiple confounders, men who consumed 2 to 4 drinks/wk (RR=0.40; 95% CI, 0.22 to 0.75; P=0.004) or 5 to 6 drinks/wk (RR=0.21; 95% CI, 0.08 to 0.56; P=0.002) at baseline had significantly reduced risks of SCD compared with those who rarely or never consumed alcohol. The relationship for SCD was U-shaped (P=0. 002), with the risk approaching unity at >/=2 drinks/d. In contrast, the relationship of alcohol intake and nonsudden CHD death was L-shaped or linear (P for trend=0.02).

CONCLUSIONS

In these prospective data, men who consumed light-to-moderate amounts of alcohol (2 to 6 drinks/wk) had a significantly reduced risk of SCD compared with those who rarely or never consumed alcohol.

Fish consumption and risk of sudden cardiac death

CONTEXT

Dietary fish intake has been associated with a reduced risk of fatal cardiac end points, but not with nonfatal end points. Dietary fish intake may have a selective benefit on fatal arrhythmias and therefore sudden cardiac death.

OBJECTIVE

To investigate prospectively the association between fish consumption and the risk of sudden cardiac death.

DESIGN

Prospective cohort study.

SETTING

The US Physicians' Health Study.

PATIENTS

A total of 20 551 US male physicians 40 to 84 years of age and free of myocardial infarction, cerebrovascular disease, and cancer at baseline who completed an abbreviated, semiquantitative food frequency questionnaire on fish consumption and were then followed up to 11 years.

MAIN OUTCOME MEASURE

Incidence of sudden cardiac death (death within 1 hour of symptom onset) as ascertained by hospital records and reports of next of kin.

RESULTS

There were 133 sudden deaths over the course of the study. After controlling for age, randomized aspirin and beta carotene assignment, and coronary risk factors, dietary fish intake was associated with a reduced risk of sudden death, with an apparent threshold effect at a consumption level of 1 fish meal per week (P for trend=.03). For men who consumed fish at least once per week, the multivariate relative risk of sudden death was 0.48 (95% confidence interval, 0.24-0.96; P=.04) compared with men who consumed fish less than monthly. Estimated dietary n-3 fatty acid intake from seafood also was associated with a reduced risk of sudden death but without a significant trend across increasing categories of intake. Neither dietary fish consumption nor n-3 fatty acid intake was associated with a reduced risk of total myocardial infarction, nonsudden cardiac death, or total cardiovascular mortality. However, fish consumption was associated with a significantly reduced risk of total mortality.

CONCLUSION

These prospective data suggest that consumption of fish at least once per week may reduce the risk of sudden cardiac death in men.

Sex differences in cardiac arrest survivors

BACKGROUND

Important sex differences in the epidemiology of sudden death and in the results of electrophysiological testing in survivors of cardiac arrest have been identified. These differences are currently poorly understood.

METHODS AND RESULTS

Three hundred fifty-five consecutive survivors of out-of-hospital cardiac arrest (84 women and 271 men) referred for electrophysiologically guided therapy were analyzed retrospectively for sex differences in underlying pathology and predictors of outcome. Women were significantly less likely to have underlying coronary artery disease than men (45% versus 80%) and more likely to have other forms of heart disease or structurally normal hearts (P<.0001). The mean left ventricular ejection fraction was higher in women (0.46+/-0.18 versus 0.41+/-0.18, P<.05), and women were more likely to have no inducible arrhythmia at baseline electrophysiological testing (46% versus 27%, P=.002), although when the patients were stratified by coronary artery disease status, these sex differences were no longer present. The independent predictors of outcome differed between men and women. In men, a left ventricular ejection fraction of <0.40 was the most powerful independent predictor of total (relative risk, 2.8; 95% CI, 1.6 to 5.0; P<.0001) and cardiac (relative risk, 6.3; 95% CI, 2.9 to 13.5; P<.0001) mortality. In contrast, the presence of coronary artery disease was the only independent predictor of total (relative risk, 4.5; 95% CI, 1.5 to 13.4; P=.003) and cardiac (relative risk, 4.4; 95% CI, 1.2 to 15.6; P=.012) mortality in women.

CONCLUSIONS

Females survivors of cardiac arrest are less likely to have underlying coronary artery disease. The predictors of total and cardiac mortality differ between male and female survivors. Coronary artery disease status is the most important predictor in women, and impaired left ventricular function is the most important predictor in men.