Sir Peter MacCallum Department of Oncology - Research Publications

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    The Development and Piloting of a Virtual Reality Patient Consultation Simulation to Improve Oncology Practitioners Communication and Counseling Skills
    Kok, DL ; Sapkaroski, D ; Dushyanthen, S ; Diggens, J ; Anderson, N ; Barrett, M ; McArthur, G (Elsevier BV, 2021-09)
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    A Phase III, randomized, open-label study (CONTACT-02) of cabozantinib plus atezolizumab versus second novel hormone therapy in patients with metastatic castration-resistant prostate cancer
    Agarwal, N ; Azad, A ; Carles, J ; Chowdhury, S ; McGregor, B ; Merseburger, AS ; Oudard, S ; Saad, F ; Soares, A ; Benzaghou, F ; Kerloeguen, Y ; Kimura, A ; Mohamed, N ; Panneerselvam, A ; Wang, F ; Pal, S (FUTURE MEDICINE LTD, 2022-01-17)
    Cabozantinib inhibits multiple receptor tyrosine kinases, including the TAM kinase family, and may enhance response to immune checkpoint inhibitors. One cohort of the ongoing phase Ib COSMIC-021 study (NCT03170960) evaluating cabozantinib plus the PD-L1 inhibitor atezolizumab in men with metastatic castration-resistant prostate cancer (mCRPC) that has progressed in soft tissue on/after enzalutamide and/or abiraterone treatment for metastatic disease has shown promising efficacy. Here, we describe the rationale and design of a phase III trial of cabozantinib plus atezolizumab versus a second novel hormone therapy (NHT) in patients who have previously received an NHT for mCRPC, metastatic castration-sensitive PC or nonmetastatic CRPC and have measurable visceral disease and/or extrapelvic adenopathy - a population with a significant unmet need for treatment options. Trial Registration Clinical Trial Registration: NCT04446117 (ClinicalTrials.gov) Registered on 24 June 2020.
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    Abstract 2862: BMP4 mediated suppression of cholesterol synthesis and breast cancer metastasis
    Anderson, RL ; Chi, LH ; Burrows, AD ; Roslan, S ; Redfern, A (American Association for Cancer Research (AACR), 2021-07-01)
    Abstract Breast cancer affects one in seven women and kills more than 600,000 women each year. Compared to the 98.9% survival rate of patients with localized breast cancer, the five-year survival rate of patients with distant metastasis is only 28.1%. Using cDNA arrays and patient datasets, we found that a protein called bone morphogenetic protein 4 (BMP4) is downregulated in highly metastatic breast cancer cells and in high-grade breast tumors. BMP4 is a ligand in the TFGβ/BMP cytokine family and has the capacity to suppress TGFβ signaling through induction of SMAD6 and SMAD7. In several different preclinical metastasis models, we have shown that restored BMP4 expression in breast cancer cells with metastatic capacity does not alter primary tumor growth but results in significantly reduced metastasis to lung, liver and spine (p< 0.01), following primary tumor resection. MDA-MB-231HM cells with or without enforced BMP4 expression were recovered from primary mammary tumors and subjected to transcriptomic profiling by RNAseq. This analysis revealed that BMP4 suppressed multiple genes involved in the cholesterol biosynthesis pathway (p=2.56×10-7) and down-regulated cholesterol levels in the tumors (p=0.042). In a patient cohort of over 2000 predominantly luminal breast cancers, we found that stage, as measured by size and lymph node status, was not altered by statin use, however statin users had less high grade tumors and more luminal A tumors. In terms of recurrence, we found a marked risk reduction in patients with luminal B tumors (p=0.014) and particularly in Her2+ luminal B tumors (p=0.045). Lung, liver and brain metastases were most reduced in statin users. Current experiments involve testing a statin therapy, with the knowledge that statins are not effective in mice, but should inhibit cholesterol synthesis in human tumors in xenograft models. In addition, we are testing an inhibitor of the nuclear receptor RORγ that has been reported to activate cholesterol synthesis through SREBP2, a master regulator of cholesterol synthesis. Citation Format: Robin L. Anderson, Lap Hing Chi, Allan D. Burrows, Suraya Roslan, Andrew Redfern. BMP4 mediated suppression of cholesterol synthesis and breast cancer metastasis [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 2862.
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    Abstract 3141: Evolution of core archetypal phenotypes in progressive high grade serous ovarian cancer
    Nath, A ; Cosgrove, P ; Copeland, B ; Mirsafian, H ; Christie, E ; Pflieger, L ; Majumdar, S ; Cristea, M ; Han, E ; Lee, S ; Wang, E ; Fereday, S ; Traficante, N ; Salgia, R ; Werner, T ; Cohen, A ; Moos, P ; Chang, J ; Bowtell, D ; Bild, A (American Association for Cancer Research (AACR), 2021-07-01)
    Abstract The evolution of resistance in high-grade serous ovarian cancer (HGSOC) cells following chemotherapy is only partially understood. To uncover phenotypic changes associated with chemotherapy resistance, we profiled single-cell RNA-sequencing (scRNA-seq) transcriptomes of HGSOC tumors collected longitudinally during patient treatment. Analysis of scRNA-seq data from two independent patient cohorts revealed that HGSOC is driven by three core archetypal phenotypes, defined as oncogenic tasks that describe the majority of the transcriptome variation. A multi-task learning approach to identify the biological tasks of each archetype identified metabolism and proliferation, cellular defense response, and DNA repair signaling. The metabolism and proliferation archetype evolved during treatment and was enriched in cancer cells from patients that received multiple-lines of treatment and had elevated tumor burden indicated by CA-125 levels. The emergence of archetypes was not consistently associated with specific whole-genome driver mutations. However, archetypes were closely associated with subclonal populations at the single-cell level, indicating that subclones within a tumor often specialize in unique biological tasks. Our study reveals the core archetypes found in progressive HGSOC and shows consistent enrichment of subclones with the metabolism archetype as resistance is acquired to multiple lines of therapy. Citation Format: Aritro Nath, Patrick Cosgrove, Benjamin Copeland, Hoda Mirsafian, Elizabeth Christie, Lance Pflieger, Sumana Majumdar, Mihaela Cristea, Ernest Han, Stephen Lee, Edward Wang, Sian Fereday, Nadia Traficante, Ravi Salgia, Theresa Werner, Adam Cohen, Phillip Moos, Jeffrey Chang, David Bowtell, Andrea Bild. Evolution of core archetypal phenotypes in progressive high grade serous ovarian cancer [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 3141.
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    PHASE 1/2 STUDY OF THOR-707 (SAR444245), A PEGYLATED RECOMBINANT NON-ALPHA IL-2, AS MONOTHERAPY AND IN COMBINATION WITH PEMBROLIZUMAB OR CETUXIMAB IN PATIENTS (PTS) WITH ADVANCED SOLID TUMORS
    Falchook, G ; Gan, H ; Fu, S ; McKean, M ; Azad, A ; Sommerhalder, D ; Wang, J ; Tan, T ; Chee, C ; Barve, M ; Lemeque, C ; Acuff, N ; Pham, H ; Mooney, J ; Wang, R ; Marina, N ; Abbadessa, G ; Meniawy, T (BMJ PUBLISHING GROUP, 2021-11-01)
    Background THOR-707 (SAR444245) is a recombinant human IL-2 molecule irreversibly bound to a PEG chain to block alpha-binding while retaining near-native affinity for beta/gamma IL-2 receptor subunits. We report updated results from the ongoing HAMMER phase 1/2 trial. Methods SAR444245 was given via IV infusion as monotherapy Q2W [A] or Q3W [B], with pembrolizumab 200mg IV Q3W [C], or Q3W with cetuximab 400mg/m2 IV on D1 then 250mg/m2 IV QW [D] after pre-medication and peri-infusion hydration. A 3+3 design was used to identify the MTD/RP2D in pts with advanced solid tumors. Key objectives included assessments of safety, efficacy, pharmacokinetics (PK) and pharmacodynamics (PD). Results 68 pts, median age 61.5 (37–78) yrs with median 3 (1–10) prior therapies enrolled. Most common tumors: melanoma (n=10), colorectal (n=11). Doses tested by cohort: [A]: 8–16 µg/kg (n=9); [B]: 8–40 µg/kg (n=29); [C]: 8–32 µg/kg (n=20); [D]: 16–24 µg/kg (n=10). The most common (>30%) AEs included pyrexia (52.5%), nausea (50.0%), flu-like symptoms (44.1%), vomiting (36.8%), chills (32.4%), fatigue (32.4%), AST elevation (30.9%). AEs generally resolved promptly with supportive care. Grade(G) 3/4 (>5%) related AEs included ALT/AST elevation (5.9%), and decreased lymphocyte count (26.5% within first 24 hrs, recovering by 48–72 hrs, this lymphocyte migration is mechanistically consistent with immune cell margination). G3/4 CRS was observed in 2 pts. Two DLTs occurred: G3 infusion reaction (32 µg/kg [B]) and G3 AST/ALT/G2 bilirubin elevation with G2 CRS (24 µg/kg [C]). No vascular leak syndrome, QTc prolongation, cardiac, or end organ toxicity was observed. Half-life was ~10 h. Sustained increases in CD8 T and NK cells were observed (fold relative to baseline): monotherapy (1–9.4x and 2–43.3x); with pembrolizumab (0.5–5.78x and 1.5–26.9x); with cetuximab (1.3–7.57x and 3.6–45.4x). Max CD4 and eosinophils increased to 136 cell/µL and 1078 cell/µL. No IL-5 elevation or ADAs were observed. Transient IL-6 increases in 4 pts (500, 627, 1000, 1100 pg/mL) were not associated with AEs. Four pts had confirmed PRs (1 PD1-treated SCC, unknown primary [B]; 2 PD1-naïve BCC and 1 PD1-treated HNSCC [C]); 3 pts had minor responses -- prostate (-24%) and PD1-treated melanoma (-17%) [B]; PD1-treated NSCLC (¬-29%) [C] -- after ≥2 scans. 23 pts completed ≥5 cycles. Conclusions SAR444245 was well tolerated and demonstrated antitumor activity in heavily pretreated patients, including prior checkpoint inhibitor therapy. Clinical safety, efficacy and PD suggest a wide therapeutic window. Combination with pembrolizumab and cetuximab leveraged SAR44245’s effects on CD8 T and NK cells. Trial Registration NCT04009681 Ethics Approval The clinical trial was approved by each institutions ethics’ and review board prior to beginning study enrollment.
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    Priority recommendations for the implementation of patient-reported outcomes in clinical cancer care: a Delphi study
    Mazariego, C ; Jefford, M ; Chan, RJ ; Roberts, N ; Millar, L ; Anazodo, A ; Hayes, S ; Brown, B ; Saunders, C ; Webber, K ; Vardy, J ; Girgis, A ; Koczwara, B (SPRINGER, 2022-02-02)
    PURPOSE: The aim of this study was to develop priority recommendations for the service level implementation of patient-reported outcomes (PROs) into clinical cancer care. METHODS: Development of draft guidance statements was informed by a literature review, the Knowledge to Action (KTA) implementation framework, and discussion with PRO experts and cancer survivors. A two-round modified Delphi survey with key stakeholders including cancer survivors, clinical and research experts, and Information Technology specialists was undertaken. Round 1 rated the importance of the statements and round 2 ranked statements in order of priority. RESULTS: Round 1 was completed by 70 participants with round 2 completed by 45 participants. Forty-seven statements were rated in round 2. In round 1, the highest agreement items (>90% agreement) included those that focused on the formation of strong stakeholder partnerships, ensuring ongoing communication within these partnerships, and the use of PROs for improvement and guidance in clinical care. Items ranked as the highest priorities in round 2 included assessment of current staff capabilities and service requirements, mapping of workflows and processes to enable collection, and using collected PROs to guide improved health outcomes. CONCLUSIONS: This stakeholder consultation process has identified key priorities in PRO implementation into clinical cancer care that include clinical relevance, stakeholder engagement, communication, and integration within the existing processes and capabilities. IMPLICATION FOR CANCER SURVIVORS: Routine adoption of PRO collection by clinical cancer services requires multiple implementation steps; of highest priority is strong engagement and communication with key stakeholders including cancer survivors.
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    CERPASS: A RANDOMIZED, CONTROLLED, OPEN-LABEL, PHASE 2 STUDY OF CEMIPLIMAB +/- RP1 IN PATIENTS WITH ADVANCED CUTANEOUS SQUAMOUS CELL CARCINOMA
    Haydon, A ; Alamgeer, M ; Brungs, D ; Collichio, F ; Khushalani, N ; Colevas, D ; Rischin, D ; Kudchadkar, R ; Chai-Ho, W ; Daniels, G ; Lutzky, J ; Lee, J ; Bowyer, S ; Migden, M ; Silk, A ; Lebbe, C ; Grob, J-J ; Melero, I ; Sheladia, P ; Bommareddy, P ; He, S ; Andreu-Vieyra, C ; Fury, M ; Hill, A (BMJ PUBLISHING GROUP, 2021-11-01)
    Background The prognosis for advanced and metastatic cutaneous squamous cell carcinoma (CSCC) remains poor for many patients with the disease despite approval of the anti-PD1 antibodies cemiplimab and pembrolizumab.1 2 RP1 is an oncolytic virus (HSV-1) that expresses a fusogenic glycoprotein (GALV-GP R-) and granulocyte macrophage colony stimulating factor (GM-CSF). In preclinical studies, RP1 induced immunogenic tumor cell death and provided potent systemic anti-tumor activity, which is further improved by combining anti-PD-1 therapy.3 Preliminary results from IGNYTE, a phase I/II clinical study of RP1 in combination with nivolumab showed a high rate of deep and durable responses in patients (pts) with CSCC.4 The objective of this trial is to evaluate the safety and efficacy of cemiplimab + RP1 versus cemiplimab alone in advanced CSCC. Methods This global, multicenter, randomized phase 2 study is enrolling pts with metastatic or unresectable, locally advanced CSCC who are not candidates for/refuse surgery and/or radiotherapy. Key eligibility criteria include no prior treatment with anti-PD1/PD-L1 antibodies or oncolytic viruses. The clinical trial will enroll approximately 180 pts from centers in the EU, Australia, Canada and USA. Pts will be randomized in a 2:1 ratio favoring the RP1 + cemiplimab arm. Pts will receive 350 mg of cemiplimab intravenously (IV) Q3W for up to 108 weeks. In the RP1 + cemiplimab arm, RP1 will be injected intratumorally at a starting RP1 dose of 1 × 10^6 plaque forming units (PFU)/mL alone, followed by up to 7 doses of RP1 at 1 × 10^7 PFU/mL Q3W together with cemiplimab. Pts in the combination arm may receive up to 8 additional RP1 doses. No crossover will be allowed. Pts will be stratified by disease status and prior systemic therapy. Tumor assessments will be performed every 9 weeks. Primary endpoints are overall response rate and complete response rate by blinded independent review. Secondary endpoints include safety, progression free survival, duration of response and overall survival. Exploratory endpoints include viral shedding and biodistribution, and immune biomarker analyses. This trial is currently enrolling pts. Trial Registration NCT04050436 References Migden MR, Rischin D, Schmults CD, Guminski A, Hauschild A, Lewis KD, Chung CH, Hernandez-Aya L, Lim AM, Chang ALS, Rabinowits G, Thai AA, Dunn LA, Hughes BGM, Khushalani NI, Modi B, Schadendorf D, Gao B, Seebach F, Li S, Li J, Mathias M, Booth J, Mohan K, Stankevich E, Babiker HM, Brana I, Gil-Martin M, Homsi J, Johnson ML, Moreno V, Niu J, Owonikoko TK, Papadopoulos KP, Yancopoulos GD, Lowy I, Fury MG. PD-1 blockade with cemiplimab in advanced cutaneous squamous-cell carcinoma. N Engl J Med 2018;379(4):341–351. Grob JJ, Gonzalez R, Basset-Seguin N, Vornicova O, Schachter J, Joshi A, Meyer N, Grange F, Piulats JM, Bauman JR, Zhang P, Gumuscu B, Swaby RF, Hughes BGM. Pembrolizumab monotherapy for recurrent or metastatic cutaneous squamous cell carcinoma: a single-arm phase II trial (KEYNOTE-629). J Clin Oncol 2020;38(25):2916–2925. Thomas S, Kuncheria L, Roulstone V, Kyula JN, Mansfield D, Bommareddy PK, Smith H, Kaufman HL, Harrington KJ, Coffin RS. Development of a new fusion-enhanced oncolytic immunotherapy platform based on herpes simplex virus type 1. J Immunother Cancer 2019;7(1):214. Middleton M, Aroldi F, Sacco J, Milhem M, Curti B, VanderWalde A, Baum S, Samson A, Pavlick A, Chesney J, Niu J, Rhodes T, Bowles T, Conry R, Olsson-Brown A, Earl Laux D, Kaufman H, Bommareddy P, Deterding A, Samakoglu S, Coffin R, Harrington K. 422 An open-label, multicenter, phase 1/2 clinical trial of RP1, an enhanced potency oncolytic HSV, combined with nivolumab: updated results from the skin cancer cohorts. J Immunother Cancer 2020; 8 (3). Ethics Approval The study was approved by institutional review board or the local ethics committee at each site. Informed consent was obtained from patients before participating into the trial.
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    The role of F-18-FDG PET/CT in retroperitoneal sarcomas-A multicenter retrospective study
    Subramaniam, S ; Callahan, J ; Bressel, M ; Hofman, MS ; Mitchell, C ; Hendry, S ; Vissers, FL ; Van Der Hiel, B ; Patel, D ; Van Houdt, WJ ; Tseng, WW ; Gyorki, DE (WILEY, 2021-01-14)
    BACKGROUND: The role of 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT) in the evaluation of retroperitoneal sarcomas is poorly defined. We evaluated the correlation of maximum standardized uptake value (SUVmax) with pathologic tumor grade in the surgical specimen of primary retroperitoneal dedifferentiated liposarcoma (DDLPS) and leiomyosarcoma (LMS). METHODS: Patients with the above histological subtypes in three participating institutions with preoperative 18 F-FDG PET/CT scan and histopathological specimen available for review were included. The association between SUVmax and pathological grade was assessed. Correlation between SUVmax and relapse-free survival (RFS) and overall survival (OS) were also studied. RESULTS: Of the total 58 patients, final pathological subtype was DDLPS in 44 (75.9%) patients and LMS in 14 (24.1%) patients. The mean SUVmax was 8.7 with a median 7.1 (range, 2.2-33.9). The tumors were graded I, II, III in 6 (10.3%), 35 (60.3%), and 17 (29.3%) patients, respectively. There was an association of higher histological grade with higher SUVmax (rs  = 0.40, p = .002). Increasing SUVmax was associated with worse RFS (p = .003) and OS (p = .003). CONCLUSION: There is a correlation between SUVmax and pathologic tumor grade; increasing SUVmax was associated with worse OS and RFS, providing a preoperative noninvasive surrogate marker of tumor grade and biological behavior.
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    Abstract 2671: SMAD4 as a potential gatekeeper for genomic instability and mTOR-mediated tumorigenesis in esophageal adenocarcinoma
    Milne, JV ; Gotovac, JR ; Fujihara, KM ; Duong, CP ; Phillips, WA ; Clemons, NJ (American Association for Cancer Research (AACR), 2021-07-01)
    Abstract Esophageal cancer is the 8th most common cancer worldwide and has the 6th highest mortality rate of all cancers. The 5-year survival rate following esophageal adenocarcinoma (EAC) diagnosis is dismal at less than 15 percent, indicating a dire need for improved therapeutic strategies and early detection. EAC develops stepwise following exposure to chronic gastric reflux: From pre-malignant Barrett's metaplasia, through stages of low- and high-grade dysplasia until developing into invasive cancer. Mutation or loss of common tumor suppressor genes TP53 and SMAD4 act as markers for cancer progression, occurring in high-grade dysplastic tissue and invasive EAC, respectively. Our novel in vivo tumorigenesis model demonstrates progression of Barrett's metaplasia to EAC, in which SMAD4-deficient Barrett's metaplasia cells form tumors in immunodeficient mice after a period of latency and in a dose-dependent manner. This delayed tumor growth onset suggests further drivers are required for oncogenesis, and these SMAD4-deficient cells and tumors display a greater degree of genomic instability than wildtype-SMAD4 controls. A genome-wide CRISPR-Cas9 knockout screen unveiled a synthetic lethal relationship between SMAD4-deficiency and cell cycle checkpoint inhibition, suggesting a role for SMAD4 in maintaining genomic stability and a potential novel therapeutic avenue for SMAD4-deficient EAC. Additionally, a concurrent in vivo CRISPR-Cas9 tumorigenesis screen produced tumors 4-fold faster than the previous model and identified regulators of mTOR signaling as co-operative drivers of tumorigenesis in EAC. Wildtype-SMAD4 cells failed to generate tumors despite undergoing the same genetic perturbations, indicating a potential gatekeeping effect of SMAD4 in mTOR-mediated EAC tumorigenesis. In sum, loss of SMAD4 acts as a double-edged sword, increasing genomic instability and thereby rendering EAC cells sensitive to cell cycle checkpoint inhibition, whilst simultaneously co-operating with modulated mTOR signaling to promote tumorigenesis in EAC xenograft models. Citation Format: Julia V. Milne, Jovana R. Gotovac, Kenji M. Fujihara, Cuong P. Duong, Wayne A. Phillips, Nicholas J. Clemons. SMAD4 as a potential gatekeeper for genomic instability and mTOR-mediated tumorigenesis in esophageal adenocarcinoma [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 2671.
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    The unexplored immune landscape of high-risk pediatric cancers.
    Mayoh, C ; Terry, RL ; Wong, M ; Lau, LM ; Khuong-Quang, DA ; Mateos, MK ; Tyrrell, V ; Haber, M ; Ziegler, DS ; Cowley, MJ ; Trapani, JA ; Neeson, PJ ; Ekert, PG (AMER ASSOC CANCER RESEARCH, 2021-07-01)
    Abstract In adult cancer, immune signatures such as the T cell-inflamed gene expression profile (GEP) have been developed to predict which patients are likely to respond to immune checkpoint inhibitors (ICIs) beyond high tumor mutation burden (TMB) and PD-L1 expression. The GEP infers T cell infiltration and activation in the tumor microenvironment (TME) from transcriptomic data. However, it is not known whether tools such as GEP are applicable in pediatric cancer, as the TME in childhood cancers is largely unexplored and response to ICIs are rare. We have undertaken an integrated analysis of the pediatric TME using RNA-sequencing (RNA-seq) and immunohistochemistry (IHC). Our goal is to identify patients with T cell-inflamed or “hot” tumors who may benefit from ICIs. Through Australia's ZERO childhood cancer precision medicine program we performed RNA-seq on 347 high-risk pediatric cancers (estimated <30% chance of survival) and performed IHC for CD4, CD8, CD45 and PD-L1 on 112 matching samples. Using both informatic assessments and IHC as independent measures of immune infiltration, we mapped the immune landscape of the TME across a broad range of high-risk pediatric cancers. As RNA-seq is increasingly used in the analysis of patient tumors, we investigated numerous molecular correlates of immune infiltration, tailored specifically to pediatric patients. RNA-seq was used to generate the GEP and map expression profiles of immune checkpoint genes, and deconvolution algorithms were used to extract the immune cell composition for every tumor. The correlation analysis between IHC, deconvolution of cell mixture composition and GEP were assessed, including PD-L1 protein and mRNA expression. We observed significant correlation between PD-L1 protein and mRNA expression and a weak correlation of CD8+ T cells with GEP. Deconvoluted TME estimates were most tightly correlated with the presence of T cell infiltrates (CD4 and CD8) with IHC. TMB and tumor purity estimates were derived from whole genome sequencing for each case. No correlation was observed between TMB and immune infiltration, however, tumor purity was negatively correlated with immune infiltration. Using IHC as an independent marker of a T cell-inflamed TME, we have identified a novel pediatric immune signature that includes markers of CD4 and CD8 T cells, T cell cytotoxicity, T and NK cell recruitment and activation, MHC Class II molecules and immune checkpoints. This is the first study to comprehensively analyze the pediatric TME in a cohort of this size and diversity, with matching IHC for orthogonal validation. Through the combination of RNA-seq and IHC, we have devised a novel immune signature specific to pediatrics and these techniques have identified a subset of patients that are immune “hot” and may potentially respond to ICIs. Conversely, we also highlight the potential of identifying immune “cold” patients who may need immunomodulatory combination strategies to maximize immune response. Citation Format: Chelsea Mayoh, Rachael L. Terry, Marie Wong, Loretta M. Lau, Dong Anh Khuong-Quang, Marion K. Mateos, Vanessa Tyrrell, Michelle Haber, David S. Ziegler, Mark J. Cowley, Joseph A. Trapani, Paul J. Neeson, Paul G. Ekert. The unexplored immune landscape of high-risk pediatric cancers [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 3044.