Patients with completely resected nongenitourinary low-risk embryonal rhabdomyosarcoma are candidates for reduced duration low-intensity chemotherapy

BACKGROUND

The survival of patients with localized embryonal rhabdomyosarcoma (RMS) completely resected at diagnosis is greater than 90%. Most patients have paratesticular, uterine, or vaginal RMS, limiting specific analyses of RMS localized in other anatomic regions. This international study was conducted to define the outcome for completely resected embryonal RMS at sites other than paratesticular, uterine, or vaginal primary sites.

METHODS

A total of 113 patients aged 0-18 years were identified who were enrolled from January 1995 to December 2016 in Children's Oncology Group (COG) (64 patients) and European protocols (49). Genitourinary nonbladder and prostate RMS were excluded. The recommended chemotherapy was vincristine and actinomycin-D (VA) for 24 weeks or ifosfamide plus VA in the European protocols and VA for 48 weeks or VA plus cyclophosphamide in the COG protocols.

RESULTS

The most common primary sites were nonparameningeal head and neck (40.7%), other (23.9%), and extremities (20.4%). In the COG studies, 42% of patients received VA and 58% VA plus cyclophosphamide. In Europe, 53% received VA and 47% ifosfamide plus VA. With a median follow-up of 97.5 months, the 5-year progression-free and overall survival was 80.0% (71.2%-86.4%) and 92.5% (85.6%-96.2%), respectively, without significant differences between chemotherapy regimens. Tumor size (< or >5 cm) significantly influenced overall survival: 96.2% (88.6%-98.8%) vs. 80.6% (59.5%-91.4%), respectively (p = .01).

CONCLUSIONS

Survival of patients with nonalveolar RMS completely resected at diagnosis is excellent among tumors arising from nonparatesticular, uterine, and vaginal sites, and patients may be treated successfully with low-intensity chemotherapy. To reduce the burden of treatment, VA for 24 weeks may be considered in children with tumors <5 cm.

Creating a data commons: The INternational Soft Tissue SaRcoma ConsorTium (INSTRuCT)

In this article, we will discuss the genesis, evolution, and progress of the INternational Soft Tissue SaRcoma ConsorTium (INSTRuCT), which aims to foster international research and collaboration focused on pediatric soft tissue sarcoma. We will begin by highlighting the current state of clinical research for pediatric soft tissue sarcomas, including rhabdomyosarcoma and non-rhabdomyosarcoma soft tissue sarcoma. We will then explore challenges and research priorities, describe the development of INSTRuCT, and discuss how the consortium aims to address key research priorities.

Rates of laboratory adverse events by course in paediatric leukaemia ascertained with automated electronic health record extraction: a retrospective cohort study from the Children's Oncology Group

BACKGROUND

Adverse events are often misreported in clinical trials, leading to an incomplete understanding of toxicities. We aimed to test automated laboratory adverse event ascertainment and grading (via the ExtractEHR automated package) to assess its scalability and define adverse event rates for children with acute myeloid leukaemia and acute lymphoblastic leukaemia.

METHODS

For this retrospective cohort study from the Children's Oncology Group (COG), we included patients aged 0-22 years treated for acute myeloid leukaemia or acute lymphoblastic leukaemia at Children's Healthcare of Atlanta (Atlanta, GA, USA) from Jan 1, 2010, to Nov 1, 2018, at the Children's Hospital of Philadelphia (Philadelphia, PA, USA) from Jan 1, 2011, to Dec 31, 2014, and at the Texas Children's Hospital (Houston, TX, USA) from Jan 1, 2011, to Dec 31, 2014. The ExtractEHR automated package acquired, cleaned, and graded laboratory data as per Common Terminology Criteria for Adverse Events (CTCAE) version 5 for 22 commonly evaluated grade 3-4 adverse events (fatal events were not evaluated) with numerically based CTCAE definitions. Descriptive statistics tabulated adverse event frequencies. Adverse events ascertained by ExtractEHR were compared to manually reported adverse events for patients enrolled in two COG trials (AAML1031, NCT01371981; AALL0932, NCT02883049). Analyses were restricted to protocol-defined chemotherapy courses (induction I, induction II, intensification I, intensification II, and intensification III for acute myeloid leukaemia; induction, consolidation, interim maintenance, delayed intensification, and maintenance for acute lymphoblastic leukaemia).

FINDINGS

Laboratory adverse event data from 1077 patients (583 from Children's Healthcare of Atlanta, 200 from the Children's Hospital of Philadelphia, and 294 from the Texas Children's Hospital) who underwent 4611 courses (549 for acute myeloid leukaemia and 4062 for acute lymphoblastic leukaemia) were extracted, processed, and graded. Of the 166 patients with acute myeloid leukaemia, 86 (52%) were female, 80 (48%) were male, 96 (58%) were White, and 132 (80%) were non-Hispanic. Of the 911 patients with acute lymphoblastic leukaemia, 406 (45%) were female, 505 (55%) were male, 596 (65%) were White, and 641 (70%) were non-Hispanic. Patients with acute myeloid leukaemia had the most adverse events during induction I and intensification II. Hypokalaemia (one [17%] of six to 75 [48%] of 156 courses) and alanine aminotransferase (ALT) increased (13 [10%] of 134 to 27 [17%] of 156 courses) were the most prevalent non-haematological adverse events in patients with acute myeloid leukaemia, as identified by ExtractEHR. Patients with acute lymphoblastic leukaemia had the greatest number of adverse events during induction and maintenance (eight adverse events with prevalence ≥10%; induction and maintenance: anaemia, platelet count decreased, white blood cell count decreased, neutrophil count decreased, lymphocyte count decreased, ALT increased, and hypocalcaemia; induction: hypokalaemia; maintenance: aspartate aminotransferase [AST] increased and blood bilirubin increased), as identified by ExtractEHR. 187 (85%) of 220 total comparisons in 22 adverse events in four AAML1031 and six AALL0923 courses were substantially higher with ExtractEHR than COG-reported adverse event rates for adverse events with a prevalence of at least 2%.

INTERPRETATION

ExtractEHR is scalable and accurately defines laboratory adverse event rates for paediatric acute leukaemia; moreover, ExtractEHR seems to detect higher rates of laboratory adverse events than those reported in COG trials. These rates can be used for comparisons between therapies and to counsel patients treated on or off trials about the risks of chemotherapy. ExtractEHR-based adverse event ascertainment can improve reporting of laboratory adverse events in clinical trials.

FUNDING

US National Institutes of Health, St Baldrick's Foundation, and Alex's Lemonade Stand Foundation.

Automated Ascertainment of Typhlitis From the Electronic Health Record

PURPOSE

Adverse events (AEs) on Children's Oncology Group (COG) trials are manually ascertained using Common Terminology Criteria for Adverse Events. Despite significant effort, we previously demonstrated that COG typhlitis reporting sensitivity was only 37% when compared with gold standard physician chart abstraction. This study tested an automated typhlitis identification algorithm using electronic health record data.

METHODS

Electronic health record data from children with leukemia age 0-22 years treated at a single institution from 2006 to 2019 were included. Patients were divided into derivation and validation cohorts. Rigorous chart abstraction of validation cohort patients established a gold standard AE data set. We created an automated algorithm to identify typhlitis matching Common Terminology Criteria for Adverse Events v5 that included antibiotics, neutropenia, and non-negated mention of typhlitis in a note. We iteratively refined the algorithm using the derivation cohort and then applied the algorithm to the validation cohort; performance was compared with the gold standard. For patients on trial AAML1031, COG AE report performance was compared with the gold standard.

RESULTS

The derivation cohort included 337 patients. The validation cohort included 270 patients (961 courses). Chart abstraction identified 16 courses with typhlitis. The algorithm identified 37 courses with typhlitis; 13 were true positives (sensitivity 81.3%, positive predictive value 35.1%). For patients on AAML1031, chart abstraction identified nine courses with typhlitis, and COG reporting correctly identified 4 (sensitivity 44.4%, positive predictive value 100.0%).

CONCLUSION

The automated algorithm identified true cases of typhlitis with higher sensitivity than COG reporting. The algorithm identified false positives but reduced the number of courses needing manual review by 96% (961 to 37) by detecting potential typhlitis. This algorithm could provide a useful screening tool to reduce manual effort required for typhlitis AE reporting.

Is Detection of Relapse by Surveillance Imaging Associated With Longer Survival in Patients With Rhabdomyosarcoma?

BACKGROUND

We investigated whether surveillance imaging had an impact on post-relapse survival in patients with rhabdomyosarcoma (RMS). We hypothesized that relapse detected by imaging (group IM) would be associated with longer survival compared with relapse detected with a clinical sign or symptom (group SS).

MATERIALS AND METHODS

We performed an observational multi-institutional study in 127 patients with relapsed RMS comparing overall survival (OS) after relapse using Kaplan-Meier and Cox proportional hazards analyses.

RESULTS

Relapse was detected in 60 (47%) group IM and 67 (53%) SS patients. Median follow-up in survivors was 4 years (range 1.0 to 16.7 y). Four-year OS rates were similar between group IM (28%, 95% confidence interval [CI]: 14%-40%) and SS (21%, 95% CI: 11%-31%) ( P =0.14). In multivariable analyses accounting for institution, age at diagnosis, time to relapse, risk group at diagnosis, and primary site, not receiving chemotherapy (hazard ratio [HR]: 6.8, 95% CI: 2.8-16.6), radiation (HR: 3, 95% CI: 1.7-5.3), or surgery (HR: 2.8, 95% CI: 1.6-4.8) after relapse were independently associated with poor OS.

CONCLUSION

These results on whether surveillance imaging provides survival benefit in patients with relapsed RMS are inconclusive. Larger studies are needed to justify current surveillance recommendations. Chemotherapy, radiotherapy and surgery to treat recurrence prolong OS.

Molecular testing of rhabdomyosarcoma in clinical trials to improve risk stratification and outcome: A consensus view from European paediatric Soft tissue sarcoma Study Group, Children's Oncology Group and Cooperative Weichteilsarkom-Studiengruppe

Rhabdomyosarcomas (RMSs) are the most common soft tissue sarcomas in children/adolescents less than 18 years of age with an annual incidence of 1-2/million. Inter/intra-tumour heterogeneity raise challenges in clinical, pathological and biological research studies. Risk stratification in European and North American clinical trials previously relied on clinico-pathological features, but now, incorporates PAX3/7-FOXO1-fusion gene status in the place of alveolar histology. International working groups propose a coordinated approach through the INternational Soft Tissue SaRcoma ConsorTium to evaluate the specific genetic abnormalities and generate and integrate molecular and clinical data related to patients with RMS across different trial settings. We review relevant data and present a consensus view on what molecular features should be assessed. In particular, we recommend the assessment of the MYOD1-LR122R mutation for risk escalation, as it has been associated with poor outcomes in spindle/sclerosing RMS and rare RMS with classic embryonal histopathology. The prospective analyses of rare fusion genes beyond PAX3/7-FOXO1 will generate new data linked to outcomes and assessment of TP53 mutations and CDK4 amplification may confirm their prognostic value. Pathogenic/likely pathogenic germline variants in TP53 and other cancer predisposition genes should also be assessed. DNA/RNA profiling of tumours at diagnosis/relapse and serial analyses of plasma samples is recommended where possible to validate potential molecular biomarkers, identify new biomarkers and assess how liquid biopsy analyses can have the greatest benefit. Together with the development of new molecularly-derived therapeutic strategies that we review, a synchronised international approach is expected to enhance progress towards improved treatment assignment, management and outcomes for patients with RMS.

Phase II Study of Selumetinib in Children and Young Adults With Tumors Harboring Activating Mitogen-Activated Protein Kinase Pathway Genetic Alterations: Arm E of the NCI-COG Pediatric MATCH Trial

PURPOSE

The NCI-COG Pediatric MATCH trial assigns patients age 1-21 years with relapsed or refractory solid tumors, lymphomas, and histiocytic disorders to phase II studies of molecularly targeted therapies on the basis of detection of predefined genetic alterations. Patients with tumors harboring mutations or fusions driving activation of the mitogen-activated protein kinase (MAPK) pathway were treated with the MEK inhibitor selumetinib.

METHODS

Patients received selumetinib twice daily for 28-day cycles until disease progression or intolerable toxicity. The primary end point was objective response rate; secondary end points included progression-free survival and tolerability of selumetinib.

RESULTS

Twenty patients (median age: 14 years) were treated. All were evaluable for response and toxicities. The most frequent diagnoses were high-grade glioma (HGG; n = 7) and rhabdomyosarcoma (n = 7). Twenty-one actionable mutations were detected: hotspot mutations in KRAS (n = 8), NRAS (n = 3), and HRAS (n = 1), inactivating mutations in NF1 (n = 7), and BRAF V600E (n = 2). No objective responses were observed. Three patients had a best response of stable disease including two patients with HGG (NF1 mutation, six cycles; KRAS mutation, 12 cycles). Six-month progression-free survival was 15% (95% CI, 4 to 34). Five patients (25%) experienced a grade 3 or higher adverse event that was possibly or probably attributable to study drug.

CONCLUSION

A national histology-agnostic molecular screening strategy was effective at identifying children and young adults eligible for treatment with selumetinib in the first Pediatric MATCH treatment arm to be completed. MEK inhibitors have demonstrated promising responses in some pediatric tumors (eg, low-grade glioma and plexiform neurofibroma). However, selumetinib in this cohort with treatment-refractory tumors harboring MAPK alterations demonstrated limited efficacy, indicating that pathway mutation status alone is insufficient to predict response to selumetinib monotherapy for pediatric cancers.

Abstract 5170: Coding and non-coding gene meta-features predict outcome in pediatric rhabdomyosarcomas

INTRODUCTION: Pediatric rhabdomyosarcoma (RMS) has varying outcomes, particularly in intermediate-risk disease (IR-RMS) due to the limited ability of clinical staging to accurately risk-stratify a large proportion of patients. This study aimed to identify prognostic signatures in IR-RMS, the clinical subgroup with the most heterogeneous outcomes, which can potentially improve risk stratification compared with routine clinicopathologic metrics. Signature performance was validated on an independent set of RMS patients.

METHODS: Prospectively obtained primary tumor specimens from 80 IR-RMS patients on Children’s Oncology Group clinical trial protocols formed the training set. Tumors from 54 RMS patients across all clinical risk groups formed the validation set. Whole transcriptome profiling was performed using oligonucleotide microarrays employing nearly 1.4 million probe selection regions (PSRs) and used to derive weighted meta-features. Accuracies of protein-coding and non-coding meta-features to predict overall (OS) and event-free (EFS) survival were compared using areas under receiver operating characteristic curves. Associated biological processes were analyzed using curated pathway analysis tools.

RESULTS: PAX-FKHR status was able to predict OS (p=0.041) and EFS (p=0.008) in the validation set, but not in the training set. Histologic subtype followed a similar predictive pattern. Cox regression on over 17,000 coding genes on the training set identified a prognostic 30-coding gene meta-feature (gMF; OS p=0.001, EFS p=0.012). A similar analysis on non-coding transcripts identified a 39-PSR meta-feature (ncMF; OS, EFS p&lt;0.001). Both gMF and ncMF were able to predict OS and EFS (p≤0.023) in the validation cohort. Based on OS, predictive accuracy of ncMF was higher than gMF (96% vs. 71%, p&lt;0.001). Analysis of biological processes using gMF showed enrichment for functions associated with musculoskeletal development and signaling pathways. Similar analysis of non-coding meta-features revealed enrichment for cellular assembly, cell cycle, apoptosis, and cancer-associated functions.

CONCLUSIONS: A non-coding RNA meta-feature was able to better predict outcome in IR-RMS than a coding gene meta-feature, where most standard clinical prognosticators failed. The meta-features were independently validated in IR and non-IR RMS. This suggests that non-coding transcripts can regulate and determine RMS biology and aggressiveness, and be used as novel prognostic indicators.

Citation Format: Anirban P. Mitra, Sheetal A. Mitra, Jonathan D. Buckley, Stephen X. Skapek, Douglas S. Hawkins, Timothy J. Triche. Coding and non-coding gene meta-features predict outcome in pediatric rhabdomyosarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5170.

Abstract 683: Identification of common germline variants associated with pediatric rhabdomyosarcoma survival: A report from the Children's Oncology Group (COG)

Background: Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and has one of the poorest survival rates among pediatric cancers, underscoring the need to identify factors which may be leveraged to improve therapeutic options for these individuals.

Methods: We carried out a genome-wide association study of overall survival (OS) and event-free survival (EFS) in 920 RMS patients from COG protocols and randomly divided them into discovery (n=642) and replication (n=278) cohorts. Genotyping was conducted using the Illumina OmniExpress or Global Screening Array and imputed using the Haplotype Reference Consortium. We used Cox proportional hazards regression to calculate an adjusted hazard ratio (aHR) and P value for each common variant (minor allele frequency [MAF]&gt;5%) for OS and EFS while adjusting for age at diagnosis, tumor stage, histological subtype, and the top five principal components. Analyses were also conducted by histological subtype: embryonal RMS (ERMS, n=544) and alveolar RMS (ARMS, n=268). Finally, we performed a meta-analysis of the results from the discovery and replication cohorts to generate a summary aHR and P value for each single nucleotide polymorphism (SNP).

Results: We identified an intergenic SNP at chr8q21.13 associated with worse RMS EFS across subtypes (aHR=2.08, P=2.80x10-9), which had consistent effects across the discovery (aHR=1.91, P=5.05x10-6) and replication (aHR=2.62, P=7.16x10-5) cohorts. This SNP lies in a region which spans the genomic binding site for GATA2 and GATA3, transcription factors that are recognized to contribute to cancer development. We also identified a significant association between a SNP at chr12q21.1 and worse EFS (aHR=2.04, P=3.35x10-8) with consistent effects across the discovery and replication cohorts. Based on data from the Genotype-Tissue Expression project (GTEx), this SNP is associated with expression of SLCO1B1, a gene which encodes a liver anion transporter linked to RMS treatment-related toxicities. In subtype-specific analyses, we identified a SNP at chr17q21.32 that was significantly associated with worse ARMS OS (129 events; aHR=3.18, P=3.12x10-8; discovery: aHR=3.19, P=6.23x10-4; replication: aHR=3.16, P=1.43x10-3). In GTEx, this SNP is associated with expression and splicing of genes including PITPNM3, KIAA0753, and MED31 across various tissues. No SNPs were significantly associated with ERMS OS or EFS.

Conclusion: In the first GWAS of RMS survival outcomes, we identified two SNPs that were significantly associated with worse EFS across RMS subtypes. Further, we identified a SNP that was associated with OS in ARMS patients, a subtype that is associated with worse outcomes. Additional investigation of the impact of these SNPs may further support their consideration for novel risk stratification protocols.

Citation Format: Bailey A. Martin-Giacalone, Michael E. Scheurer, Javed Khan, Stephen J. Chanock, Shengchao Alfred Li, Meredith Yeager, Deborah A. Marquez-Do, Donald A. Barkauskas, David Hall, Matthew T. McEvoy, Melissa A. Richard, Pagna Sok, Austin L. Brown, Aniko Sabo, Stephen X. Skapek, Douglas S. Hawkins, Rajkumar Venkatramani, Lisa Mirabello, Philip J. Lupo. Identification of common germline variants associated with pediatric rhabdomyosarcoma survival: A report from the Children's Oncology Group (COG) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 683.

Clinical group and modified TNM stage for rhabdomyosarcoma: A review from the Children's Oncology Group

The Children's Oncology Group (COG) uses Clinical Group (CG) and modified Tumor Node Metastasis (TNM) stage to classify rhabdomyosarcoma (RMS). CG is based on surgicopathologic findings and is determined after the completion of initial surgical procedure(s) but prior to chemotherapy and/or radiation therapy. The modified TNM stage is based on clinical and radiographic findings and is assigned prior to any treatment. These systems have evolved over several decades. We review the history, evolution, and rationale behind the current CG and modified TNM classification systems used by COG for RMS. Data from the seven most recently completed and reported frontline COG trials (D9602, D9802, D9803, ARST0331, ARST0431, ARST0531, ARST08P1) were analyzed, and confirm that CG and modified TNM stage remain relevant and useful for predicting prognosis in RMS. We propose updates based on recent data and discuss factors warranting future study to further optimize these classification systems.

Outcomes following preoperative chemoradiation +/- pazopanib in non-rhabdomyosarcoma soft tissue sarcoma (NRSTS): A report from Children's Oncology Group (COG) and NRG Oncology

11504

Background: Pazopanib is a multi-targeted tyrosine kinase inhibitor (TKI) with activity in advanced soft tissue sarcoma. ARST1321 was a phase II study designed to compare the near complete pathologic response rate (≥ 90% necrosis) following preoperative chemoradiation +/- pazopanib in children and adults with intermediate/high risk chemotherapy-sensitive body wall/extremity NRSTS. Enrollment was stopped early following a predetermined interim analysis that found the rate of near complete pathologic response to be significantly greater with the addition of pazopanib. As a planned secondary analysis of the study, we now report the outcome data for this cohort. Methods: ARST1321 was a jointly designed COG and NRG Oncology study open to enrollment July 2014-October 2018. Eligible adult (≥18 years) and pediatric (< 18 years) patients with newly-diagnosed unresected body wall/extremity NRSTS were enrolled into the Chemotherapy Cohort (> 5 cm, FNCLCC grade 2/3, protocol-designated chemotherapy-sensitive histology). Following a dose-finding phase, patients were randomized to receive (Regimen A) or not receive (Regimen B) pazopanib (< 18 years: 350 mg/m2/day; ≥ 18 years: 600 mg/day) in combination with ifosfamide (7.5 gm/m2/cycle) and doxorubicin (75 mg/m2/cycle) + 45 Gy preoperative RT followed by primary resection at week 13, then further chemotherapy to week 25. Results: Eighty-five eligible patients were enrolled in the Chemotherapy Cohort and randomized to receive or not receive pazopanib. Median age 22.1 years (range: 5.7-64.2 years); 30 patients < 18 years. Most common histologies were synovial sarcoma (n = 42) and undifferentiated pleomorphic sarcoma (n = 19). As of December 31, 2021, at a median survivor follow-up of 3.3 years (range: 0.1 – 5.8 years), the 3-year event-free survival (EFS) for all patients in the intent-to-treat analysis was 52.5% (95% CI: 34.8%-70.2%) for Regimen A and 50.6% (32%-69.2%) for Regimen B (p = 0.8677); 3-year overall survival (OS) was 75.7% (59.7%-91.7%) for Regimen A and 65.4% (48.1%-82.7%) for Regimen B (p = 0.1919). Conclusions: Although the rate of near complete pathologic response was significantly greater with the addition of pazopanib to preoperative chemoradiation in children and adults with intermediate/high risk body wall/extremity NRSTS, outcomes were not statistically significantly different between the two regimens. Pathologic response could be a TKI-related phenomenon and may not be a good surrogate marker of outcome in future studies. Clinical trial information: NCT02180867.

Ulixertinib in patients with tumors with MAPK pathway alterations: Results from NCI-COG Pediatric MATCH trial Arm J (APEC1621J)

3009

Background: The NCI-Children’s Oncology Group (COG) Pediatric Molecular Analysis for Therapy Choice (MATCH) trial assigns patients age 1 to 21 years with relapsed or refractory solid tumors, lymphomas, and histiocytic disorders to phase 2 treatment arms of molecularly-targeted therapies based on genetic alterations detected in their tumor. Arm J evaluated the ERK1/2 inhibitor ulixertinib (BVD-523FB) in patients whose tumors harbored activating alterations in the MAPK pathway ( ARAF, BRAF, HRAS, KRAS, NRAS, MAPK1, MAP2K1, GNA11, GNAQ hotspot mutations; NF1inactivating mutations; BRAF fusions). Methods: As there were no prior pediatric data, ulixertinib was initially tested in a dose escalation cohort using a rolling 6 design to establish the recommended phase 2 dose (RP2D) before proceeding with enrollment to the phase 2 cohort. Ulixertinib was administered at 260 mg/m2/dose PO BID (dose level 1, DL1, n = 15) or 350 mg/m2/dose PO BID (dose level 2, DL2, n = 5). Patients were treated on continuous 28-day cycles for up to 2 years, until disease progression or intolerable toxicity; response assessment occurred every 2-3 cycles. The primary endpoint was objective response rate; secondary endpoints included safety/tolerability and progression-free survival (PFS). Results: Twenty patients (median age 12 years; range 5-20) were enrolled between November 2018 and March 2021. All patients were evaluable for response. High-grade glioma (HGG, n = 7) was most common, with CNS tumors comprising 55% (11/20) of diagnoses; all CNS tumors except one (HGG with KRAS and NF1 mutations) harbored BRAF fusions or V600 mutations. Rhabdomyosarcoma (n = 5) was the most frequent non-CNS diagnosis, with NRAS mutations detected in 4 tumors. DL1 was declared the RP2D after first-cycle dose limiting toxicities (DLTs) occurred in 1/6 DLT-evaluable patients at DL1 and 2/5 patients at DL2 in the dose escalation cohort. Any-cycle DLTs in 8 patients in the dose escalation and primary cohorts included fatigue, anorexia, rash, nausea, vomiting, diarrhea, dehydration, increased creatinine, hypoalbuminemia, hypernatremia, and hip fracture. No objective responses were observed. Six-month PFS was 37% (95% CI: 17%, 58%). Three patients with CNS tumors achieved stable disease > 6 months (HGG with BRAF fusion, 15 cycles; glioneuronal tumor with BRAF V600E, 9 cycles; low-grade glioma with BRAF fusion, 7 cycles). Analyses of correlative studies, including pharmacokinetics and circulating tumor DNA, are ongoing. Conclusions: The pediatric RP2D of ulixertinib was established as 260 mg/m2/dose PO BID. There were no objective responses in this cohort of children and young adults with treatment-refractory tumors with activating MAPK alterations. Clinical benefit of prolonged disease control was observed in 3 patients with BRAF-altered gliomas and glioneuronal tumors. Clinical trial information: NCT03698994.

Tazemetostat in patients with tumors with alterations in EZH2 or the SWI/SNF complex: Results from NCI-COG Pediatric MATCH trial Arm C (APEC1621C)

10009

Background: The NCI-Children’s Oncology Group (COG) Pediatric Molecular Analysis for Therapy Choice (MATCH) trial assigns patients, age 1-21 years, with relapsed or refractory solid tumors, lymphomas, and histiocytic disorders to phase 2 treatment arms based on genetic alterations detected in their tumor. Arm C evaluated the EZH2 inhibitor tazemetostat in patients whose tumors harbored EZH2 hotspot mutations or SMARCB1 or SMARCA4 loss by immunohistochemistry. Methods: Tazemetostat 1200 mg/m2/dose PO BID was administered to the first 13 patients; after study amendment due to second malignancy noted in the pediatric phase 1 trial, the dose for patients with non-CNS tumors was reduced to 520 mg/m2/dose PO BID. Patients were treated for 28-day cycles until PD or intolerable toxicity (max 26 cycles); response assessments occurred every 2-3 cycles. Primary and secondary endpoints were ORR and PFS, respectively. Results: Twenty eligible and evaluable patients (median age 5 years; range 1-21) were enrolled between Nov 2017 and Sept 2020. SMARCB1 loss was detected in 16/20 (80%) tumors: atypical teratoid rhabdoid tumor (ATRT, n = 8), malignant rhabdoid tumor (MRT, n = 4), epithelioid sarcoma (ES, n = 2), renal medullary carcinoma (RMC, n = 1) and hepatocellular carcinoma (HCC, n = 1). EZH2 mutations were identified in 3/20 (15%) tumors: Ewing sarcoma (n = 2), ependymoma (n = 1). One patient with Langerhans cell histiocytosis (LCH) had SMARCA4 loss. Centrally reviewed, one objective response (PR) was observed (LCH [SMARCA4], 26 cycles at 1200 mg/m2/dose BID). Five other patients had a best response of stable disease (ES [SMARCB1], 26 cycles, 520 mg/m2/dose BID; ATRT [SMARCB1], 13 cycles,1200 mg/m2/dose BID; RMC [SMARCB1], 12 cycles, 520 mg/m2/dose BID; ES [SMARCB1], 9 cycles,1200 mg/m2/dose BID; ATRT [SMARCB1], 6 cycles, 1200 mg/m2/dose BID). No other patients received > 2 cycles. Six-month PFS was 35% (95% CI 15.7%, 55.2%); OS was 45% (95% CI 23.1%, 64.7%). Treatment-related adverse events were consistent with AEs previously reported with tazemetostat, including anemia, thrombocytopenia, elevated LFTs, abdominal pain, dyspnea, infection, and intracranial hemorrhage. Three patients had bromide elevations. Conclusions: In this cohort of children with relapsed tumors harboring EZH2 mutations or loss of SMARCB1 or SMARCA4, tazemetostat did not produce significant objective responses (ORR: 5%, 90% CI 1%, 20%). However, we observed prolonged stable disease of > 6 months (range: 6-26 cycles) in 33% of patients across different histologic diagnoses, including two patients who received the full two years of study therapysuggesting a potential effect of tazemetostat on disease stabilization. Future studies will incorporate tazemetostat in combination with chemotherapy or immunologic agents for patients with these aggressive and difficult to treat tumors. Clinical trial information: NCT03213665.

Phase 2 study to evaluate palbociclib in combination with irinotecan and temozolomide in pediatric patients with recurrent or refractory Ewing sarcoma

TPS11583

Background: Palbociclib (PD-0332991) is a highly selective, reversible, small molecule inhibitor of cyclin-dependent kinases (CDK) 4 and 6, administered orally. Functional dependence of Ewing Sarcoma (EWS) cell lines and tumor xenografts on Cyclin D1/CDK4 via genetic knockdown has shown both Cyclin D1 and CDK4 as critical dependencies for EWS cell line proliferation. The phase 1 portion of the study established the recommended Phase 2 dose (RP2D) with two chemotherapy backbones in children with solid tumors. The Phase 2 portion of the study now enrolls patients with EWS. The primary objective of this portion of the study is to determine whether the addition of palbociclib to irinotecan (IRN) and temozolomide (TMZ) will prolong event-free survival (EFS) of pediatric and young adult patients with recurrent or refractory EWS. Methods: Patients with recurrent or refractory EWS are randomized 2:1 to receive either palbociclib in combination with IRN and TMZ or IRN and TMZ alone. Randomization is stratified by type and time of disease recurrence (primary refractory or 1st recurrence <2 years vs. 1st recurrence ≥2 years or 2nd or greater recurrence). The primary efficacy endpoint is EFS per investigator assessment. Secondary efficacy endpoints include objective response, progression-free survival and overall survival. An interim futility analysis will be conducted to allow for early stopping of the study due to futility/no signal of activity based on the primary endpoint of EFS. Safety and planned interim efficacy data will be assessed by an Independent Data Monitoring Committee (DMC). Key eligibility criteria include: recurrent or refractory EWS with evaluable disease, no known bone marrow metastases, histopathological confirmation of EWSR1-ETS or FUS-ETS rearrangement or availability of formalin fixed paraffin embedded (FFPE) tumor tissue sample for central testing, age ≥2 and <21 years at the time of study entry. Treatment intervention: Patients randomized to palbociclib with IRN and TMZ treatment arm will receive palbociclib at the RP2D of 75 mg/m2 orally (either as a capsule or oral solution) once daily on Days 1-14 of each 21-day treatment cycle. TMZ will be administered orally once daily at 100 mg/m2 on Days 1-5 (intravenously (IV) if patient cannot swallow the TMZ capsule). IRN will be administered IV at 50 mg/m2 on Days 1-5. Patients randomized to the chemotherapy only treatment arm will receive IRN and TMZ at the same doses on Days 1-5 of the 21-day treatment cycle. Treatment will continue until disease progression, patient and/or legal guardian refusal, unacceptable toxicity , or up to 24 months of treatment, whichever occurs first. The Phase 2 enrolment has been initiated and 1/75 patients has been enrolled as of Jan 2022. Clinical trial information: NCT03709680.

An updated assessment of 43,110 patients enrolled in the Childhood Cancer Research Network: A Children's Oncology Group report

BACKGROUND

The Childhood Cancer Research Network (CCRN) was established by the Children's Oncology Group (COG) as a resource for epidemiologic studies of childhood cancer. The objective of this study was to evaluate the representativeness of CCRN and identify factors associated with enrollment.

METHOD

The number of US childhood patients with cancer diagnosed <20 years of age enrolled in CCRN (2008-2015) was compared to expected counts, calculated from Surveillance, Epidemiology, and End Results incidence rates and US Census population estimates. Observed-to-expected ratios and corresponding 95% confidence intervals (CI) were estimated across sex, race, diagnosis age, calendar year, and cancer diagnosis groups. Multivariable linear regression models were generated to evaluate the association between open COG phase 3 therapeutic trials and CCRN enrollment rates.

RESULT

The 43,110 cases enrolled in CCRN represented 36% of the expected childhood cancers diagnosed from 2008 to 2015 (N = 120,118). CCRN enrollment ratios [95% CI] were highest among males (0.38 [95% CI, 0.37-0.38]), non-Hispanics (0.35 [95% CI, 0.35-0.36]), and those diagnosed from 1 to 4 years of age (0.50 [95% CI, 0.50-51]). Enrollment ratios varied by diagnosis group, with leukemia, myeloproliferative diseases, myelodysplastic diseases (0.55 [95% CI, 0.54-0.55]), and renal tumors (0.55 [95% CI, 0.53-0.58]) having the highest enrollment. After adjusting for year of diagnosis and cancer diagnosis, there was a 3.1% [95% CI, 0.6-5.6%] increase in CCRN enrollment during windows of open COG therapeutic trials.

CONCLUSIONS

Despite enrolling only 36% of newly diagnosed cases, CCRN remains a valuable resource for investigators conducting childhood cancer etiology and survivorship research. The results of this study may inform efforts to improve enrollment on current and future COG nontherapeutic registry protocols.

Congenital spindle cell rhabdomyosarcoma: An international cooperative analysis

BACKGROUND

Spindle cell rhabdomyosarcoma (RMS) is a rare variant of RMS accounting for up to 10% of cases in infants. In older children and adults, spindle cell RMS is associated with MYOD1 mutations and a poor prognosis. In infants, it is associated with recurring fusions involving NCOA2 and VGLL2. Reports in the literature suggest a favorable prognosis for this subset, however, little is known about treatment and outcome data of infants with spindle cell RMS.

METHODS

Characteristics, treatment, and outcome of an international cohort of 40 patients aged ≤ 12 months with spindle cell RMS treated from 1997 to 2018 were evaluated.

RESULTS

Localized disease (LD) was diagnosed in 39 patients. The median age at diagnosis was 2.5 months (range 0-12 months). Expert pathologic review confirmed the diagnosis of spindle cell RMS in all patients. Among 26 tumors that had molecular evaluation, 13 had rearrangements of NCOA and/or VGLL. Multimodal treatment of infants with LD included conventional (age adjusted) chemotherapy (n = 37), resection (n = 31) and radiotherapy (RT) (n = 5, brachytherapy in 3). Complete remission was achieved in 37/39 patients. Progressive disease occurred in two infants, relapsed disease in three. Microscopically complete surgical resection was associated with five-year event-free survival (EFS) and overall survival (OS) of 100%. Two patients with tumors ≤ 5 cm were treated with microscopically complete resection only and were alive 1 and 4.2 years after diagnosis. The 5-year EFS and OS for infants with LD were 86% (±11; CI 95%) and 91% (±9; CI 95%), respectively. One patient had metastatic disease (NCOA fusion positive) with primary tumor in head and neck and brain metastases. This patient died despite chemotherapy and delayed resection of the primary tumor due to respiratory failure secondary to cytomegalovirus infection 1.2 years after diagnosis.

CONCLUSION

Infants with spindle cell RMS have an excellent prognosis. Multimodal treatment including microscopically complete resection of the tumor is strongly recommended.

The effects of pazopanib on doxorubicin pharmacokinetics in children and adults with non-rhabdomyosarcoma soft tissue sarcoma: a report from Children's Oncology Group and NRG Oncology study ARST1321

PURPOSE

The use of tyrosine kinase inhibitors for the treatment for soft tissue sarcomas is increasing given promising signals of activity in a variety of tumor types. The recently completed study in non-rhabdomyosarcoma soft tissue sarcomas, ARST1321, demonstrated that the addition of pazopanib to neoadjuvant ifosfamide, doxorubicin, and radiation improved the pathological near complete response rate compared with chemoradiotherapy alone. Pharmacokinetic (PK) evaluation of doxorubicin with pazopanib has not been previously reported. As an exploratory aim, doxorubicin PK data were collected during the dose-finding phase of the study in patients receiving chemotherapy and pazopanib to assess the effect of pazopanib on doxorubicin PK parameters.

METHODS

Blood samples were collected during cycle 2 (week 4) of chemotherapy at the following time points from doxorubicin administration: predose, 5, 30, and 60 min, and 2, 4, 8, 24 ± 3, and 48 ± 3 h after dosing. The population pharmacokinetic and individual post hoc estimates of doxorubicin and doxorubicinol were determined by nonlinear mixed-effects modeling.

RESULTS

There were 52 doxorubicin and doxorubicinol samples from 7 individuals in this study (median age: 17 years; range 14-23). The doxorubicin clearance was 26.9 (16.1, 36.4, and 33.9) L/h/m2 (post hoc median and range) and 25.8 (23.3%) L/h/m2 [population estimate and IIV (CV%)]. The doxorubicinol apparent clearance was 67.5 (18.2, 1701) L/h/m2 (post hoc median and range) and 58.7 (63.7%) L/h/m2 [population estimate and IIV (CV%)].

CONCLUSION

The PK data of seven patients treated on ARST1321 is consistent with previously reported population and post hoc doxorubicin clearance and doxorubicinol apparent clearance estimates, showing that the addition of pazopanib does not significantly alter doxorubicin pharmacokinetics. These data support the safety of administration of pazopanib with doxorubicin-containing chemotherapy.

An update on rhabdomyosarcoma risk stratification and the rationale for current and future Children's Oncology Group clinical trials

Children and adolescents with rhabdomyosarcoma (RMS) comprise a heterogeneous population with variable overall survival rates ranging between approximately 6% and 100% depending on defined risk factors. Although the risk stratification of patients has been refined across five decades of collaborative group studies, molecular prognostic biomarkers beyond FOXO1 fusion status have yet to be incorporated prospectively in upfront risk-based therapy assignments. This review describes the evolution of risk-based therapy and the current risk stratification, defines a new risk stratification incorporating novel biomarkers, and provides the rationale for the current and upcoming Children's Oncology Group RMS studies.

Actionable Tumor Alterations and Treatment Protocol Enrollment of Pediatric and Young Adult Patients With Refractory Cancers in the National Cancer Institute-Children's Oncology Group Pediatric MATCH Trial

PURPOSE

The National Cancer Institute-Children's Oncology Group Pediatric MATCH trial aimed to facilitate evaluation of molecular-targeted therapies in biomarker-selected cohorts of childhood and young adult patients with cancer by screening tumors for actionable alterations.

PATIENTS AND METHODS

Tumors from patients age 1-21 years with refractory solid tumors, lymphomas, or histiocytic disorders were subjected to cancer gene panel sequencing and limited immunohistochemistry to identify actionable alterations for assignment to phase II treatment arms. The rates of treatment arm assignment and enrollment were compared between clinical and demographic groups.

RESULTS

Testing was completed for 94.7% of tumors submitted. Actionable alterations were detected in 31.5% of the first 1,000 tumors screened, with treatment arm assignment and enrollment occurring in 28.4% and 13.1% of patients, respectively. Assignment rates varied by tumor histology and were higher for patients with CNS tumors or enrolled at Pediatric Early Phase Clinical Trials Network sites. A reported history of prior clinical molecular testing was associated with higher assignment and enrollment rates. Actionable alterations in the mitogen-activated protein kinase signaling pathway were most frequent (11.2%). The most common reasons provided for not enrolling on treatment arms were patients receiving other treatment or poor clinical status.

CONCLUSION

The Pediatric MATCH trial has proven the feasibility of a nationwide screening Protocol for identification of actionable genetic alterations and assignment of pediatric and young adult patients with refractory cancers to trials of molecularly targeted therapies. These data support the early use of tumor molecular screening for childhood patients with cancer whose tumors have not responded to standard treatments.

Rising drug cost impacts on cost-effectiveness of 2 chemotherapy regimens for intermediate-risk rhabdomyosarcoma: A report from the Children's Oncology Group

BACKGROUND

The Children's Oncology Group clinical trial for intermediate risk rhabdomyosarcoma randomized participants to a combination of vincristine, dactinomycin, and cyclophosphamide (VAC) alone or VAC alternating with vincristine plus irinotecan (VAC/VI). Clinical outcomes were similar, but toxicity profiles differed. This study estimates the cost differences between arms from the health care system's perspective.

METHODS

A decision-analytic model was used to estimate the incremental cost-effectiveness ratio (ICER) of VAC versus VAC/VI. Protocol-required or recommended medications and laboratory studies were included. Costs were obtained from national databases or supporting literature and inflated to 2019 US dollars. Demographic and outcome data were obtained from the clinical trial and directed chart reviews. Life-years (LY) were estimated from life-expectancy tables and discounted by 3% annually. Probabilistic sensitivity analyses and alternative clinical scenarios identified factors driving costs.

RESULTS

Mean direct medical costs of VAC and VAC/VI were $164,757 and $102,303, respectively. VAC was associated with an additional 0.97 LY and an ICER of $64,386/LY compared with VAC/VI. The ICER was sensitive to survival estimations and to alternative clinical scenarios including outpatient cyclophosphamide delivery (ICER $49,037/LY) or substitution of alternative hematopoietic growth factor schedules (ICER $73,191-$91,579/LY). Applying drug prices from 2012 decreased the total costs of VAC by 20% and VAC/VI by 15% because of changes in dactinomycin and pegfilgrastim prices.

CONCLUSIONS

Neither arm was clearly more cost-effective. Pharmaceutical pricing and location of treatment drove costs and may inform future treatment decisions. Rising pharmaceutical costs added $30,000 per patient, a finding important for future drug-pricing policy decisions.

LAY SUMMARY

Two chemotherapy regimens recently tested side-by-side for rhabdomyosarcoma had similar tumor outcomes, but different side effects. The health care costs of each regimen were compared; neither was clearly more cost-effective. However, the costs of each treatment changed dramatically with choices of supportive medicines and location of treatment. Costs of treatment rose by 15% to 20% because of rising US drug costs not associated with the clinical trial.

Phase III Trial Adding Vincristine-Topotecan-Cyclophosphamide to the Initial Treatment of Patients With Nonmetastatic Ewing Sarcoma: A Children's Oncology Group Report

PURPOSE

The primary aim of this phase III randomized trial was to test whether the addition of vincristine, topotecan, and cyclophosphamide (VTC) to interval compressed chemotherapy improved survival outcomes for patients with previously untreated nonmetastatic Ewing sarcoma.

METHODS

Patients were randomly assigned to receive standard five-drug interval compressed chemotherapy (regimen A) for 17 cycles or experimental therapy with five cycles of VTC within the 17 cycles (regimen B). Patients were stratified by age at diagnosis (< 18 years and ≥18 years) and tumor site (pelvic bone, nonpelvic bone, and extraosseous). Tumor volume at diagnosis was categorized as < 200 mL or ≥ 200 mL. Local control occurred following six cycles. Histologic response was categorized as no viable or any viable tumor. Event-free survival (EFS) and overall survival (OS) were compared between randomized groups with stratified log-rank tests.

RESULTS

Of 642 enrolled patients, 309 eligible patients received standard and 320 received experimental therapy. The 5-year EFS and OS were 78% and 87%, respectively. There was no difference in survival outcomes between randomized groups (5-year EFS regimen A v regimen B, 78% v 79%; P = .192; 5-year OS 86% v 88%; P = .159). Age and primary site did not affect the risk of an EFS event. However, age ≥ 18 years was associated with an increased risk of death at 5 years (hazard ratio 1.84; 95% CI, 1.15 to 2.96; P = .009). The 5-year EFS rates for patients with pelvic, nonpelvic bone, and extraosseous primary tumors were 75%, 78%, and 85%, respectively. Tumor volume ≥ 200 mL was significantly associated with lower EFS.

CONCLUSION

While VTC added to five-drug interval compressed chemotherapy did not improve survival, these outcomes represent the best survival estimates to date for patients with previously untreated nonmetastatic Ewing sarcoma.

Outcome of patients with relapsed or progressive Ewing sarcoma enrolled on cooperative group phase 2 clinical trials: A report from the Children's Oncology Group

SevenChildren's Oncology Group phase 2 trials for patients with relapsed/progressive solid tumors were analyzed to estimate the event-free survival (EFS) for relapsed/progressive Ewing sarcoma. One hundred twenty-eight Ewing sarcoma patients were enrolled and 124 events occurred. The 6-month EFS was 12.7%, demonstrating the poor outcome of these patients. Only docetaxel achieved its protocol-specified radiographic response rate for activity; however, the EFS for docetaxel was similar to other agents, indicating that a higher radiographic response rate may not translate into superior disease control. This EFS benchmark could be utilized as an additional endpoint in trials for recurrent Ewing sarcoma.

Paediatric Strategy Forum for medicinal product development of chimeric antigen receptor T-cells in children and adolescents with cancer: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

The seventh multi-stakeholder Paediatric Strategy Forum focused on chimeric antigen receptor (CAR) T-cells for children and adolescents with cancer. The development of CAR T-cells for patients with haematological malignancies, especially B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), has been spectacular. However, currently, there are scientific, clinical and logistical challenges for use of CAR T-cells in BCP-ALL and other paediatric malignancies, particularly in acute myeloid leukaemia (AML), lymphomas and solid tumours. The aims of the Forum were to summarise the current landscape of CAR T-cell therapy development in paediatrics, too identify current challenges and future directions, with consideration of other immune effector modalities and ascertain the best strategies to accelerate their development and availability to children. Although the effect is of limited duration in about half of the patients, anti-CD19 CAR T-cells produce high response rates in relapsed/refractory BCP-ALL and this has highlighted previously unknown mechanisms of relapse. CAR T-cell treatment as first- or second-line therapy could also potentially benefit patients whose disease has high-risk features associated with relapse and failure of conventional therapies. Identifying patients with very early and early relapse in whom CAR T-cell therapy may replace haematopoietic stem cell transplantation and be definitive therapy versus those in whom it provides a more effective bridge to haematopoietic stem cell transplantation is a very high priority. Development of approaches to improve persistence, either by improving T cell fitness or using more humanised/fully humanised products and co-targeting of multiple antigens to prevent antigen escape, could potentially further optimise therapy. Many differences exist between paediatric B-cell non-Hodgkin lymphomas (B-NHL) and BCP-ALL. In view of the very small patient numbers with relapsed lymphoma, careful prioritisation is needed to evaluate CAR T-cells in children with Burkitt lymphoma, primary mediastinal B cell lymphoma and other NHL subtypes. Combination trials of alternative targets to CD19 (CD20 or CD22) should also be explored as a priority to improve efficacy in this population. Development of CD30 CAR T-cell immunotherapy strategies in patients with relapsed/refractory Hodgkin lymphoma will likely be most efficiently accomplished by joint paediatric and adult trials. CAR T-cell approaches are early in development for AML and T-ALL, given the unique challenges of successful immunotherapy actualisation in these diseases. At this time, CD33 and CD123 appear to be the most universal targets in AML and CD7 in T-ALL. The results of ongoing or planned first-in-human studies are required to facilitate further understanding. There are promising early results in solid tumours, particularly with GD2 targeting cell therapies in neuroblastoma and central nervous system gliomas that represent significant unmet clinical needs. Further understanding of biology is critical to success. The comparative benefits of autologous versus allogeneic CAR T-cells, T-cells engineered with T cell receptors T-cells engineered with T cell receptor fusion constructs, CAR Natural Killer (NK)-cell products, bispecific T-cell engager antibodies and antibody-drug conjugates require evaluation in paediatric malignancies. Early and proactive academia and multi-company engagement are mandatory to advance cellular immunotherapies in paediatric oncology. Regulatory advice should be sought very early in the design and preparation of clinical trials of innovative medicines, for which regulatory approval may ultimately be sought. Aligning strategic, scientific, regulatory, health technology and funding requirements from the inception of a clinical trial is especially important as these are very expensive therapies. The model for drug development for cell therapy in paediatric oncology could also involve a 'later stage handoff' to industry after early development in academic hands. Finally, and very importantly, strategies must evolve to ensure appropriate ease of access for children who need and could potentially benefit from these therapies.

Pharmacogenomic associations of cyclophosphamide pharmacokinetic candidate genes with event-free survival in intermediate-risk rhabdomyosarcoma: A report from the Children's Oncology Group

BACKGROUND

In vitro data suggest that the growth of rhabdomyosarcoma (RMS) cells is suppressed in a concentration-dependent manner by 4-hydroxycyclophosphamide (4HCY), the principal precursor to the cytotoxic metabolite of cyclophosphamide (CY). Various retrospective studies on the relationship between genes encoding proteins involved in the formation and elimination of 4HCY (i.e., 4HCY pharmacokinetics) and cyclophosphamide (CY) efficacy and toxicity have been conflicting.

PROCEDURES

We evaluated germline pharmacogenetics in 262 patients with newly diagnosed intermediate-risk RMS who participated in one prospective Children's Oncology Group clinical trial, ARST0531. Patients were treated with either vincristine/actinomycin/cyclophosphamide (VAC) or VAC alternating with vincristine/irinotecan (VAC/VI). We analyzed the associations between event-free survival and 394 single-nucleotide polymorphisms (SNP) in 14 drug metabolizing enzymes or transporters involved in 4HCY pharmacokinetics.

RESULTS

Eight SNPs were associated (p-value < .05 by univariate analysis) with 3-year event-free survival; no SNPs survived a false discovery rate < 0.05.

CONCLUSIONS

Our data suggest that a pharmacogenomic approach to therapy personalization of cyclophosphamide in intermediate-risk rhabdomyosarcoma is not viable. Other methods to personalize therapy should be explored.

Clinical Outcomes of Diffuse Sclerosing Variant Papillary Thyroid Carcinoma in Pediatric Patients

OBJECTIVES/HYPOTHESIS

The diffuse sclerosing variant of papillary thyroid carcinoma (DSV) may be more aggressive than conventional well-differentiated non-DSV related papillary thyroid carcinomas (N-PTC).

STUDY DESIGN

Retrospective chart review.

METHODS

Retrospective review of clinical outcomes for patients 21 years of age or younger who underwent initial surgery for PTC at a single institution from January 1, 2005 to April 1, 2020. Genomic analysis was performed using targeted next-generation sequencing. Data were analyzed using Fischer's exact test and Kaplan-Meier curve log-rank test.

RESULTS

Our cohort consisted of 72 patients, nine with DSV and 63 with N-PTC. Age at diagnosis was comparable (15.4 vs. 16.2 years, respectively, P = .46). DSV were more likely to be in the high-risk American Thyroid Academy pediatric risk group (100% vs. 41.3%, P = .004), to present with regional cervical lymph node metastases (100% vs. 60.3%, P = .036), and to present with distant metastases (67% vs. 22%, P = .005). No mortality seen in either group over 27.5 (interquartile range 14.8, 46.00) months average follow-up. Throughout the follow-up period, DSV were more likely to experience progression than N-PTC (hazard ratio = 5.7 [95% confidence interval 1.7-20.0; P = .0056]). In a subset of 19 patients with aggressive disease who had molecular testing as part of clinical care we detected RET fusions in nearly all DSV compared to a minority of N-PTC (83% vs. 15.4%, P = .0095).

CONCLUSIONS

Pediatric patients with DSV have more advanced disease at diagnosis and are more likely to experience progression of disease compared to patients with N-PTC. The prevalence of RET fusions in our cohort recapitulates the frequency of this alteration described in prior studies.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.