P01.001.A Hypoxia-mimetic agent DFO inhibits cancer cell proliferation and induces DNA damage

David Diez-Castro 1;2, Luis Perez-Romasanta3, Rogelio González-Sarmiento1;2;4, Ana-Belén Herrero1;2;4 1Institute of Biomedical Research of Salamanca, Institute of Biomedical Research of Salamanca, Salamanca; 2Faculty of Medicine, Departament of Medicine, Salamanca; 3Hospital University of Salamanca, Oncology service, Salamanca; 4Institute of Molecular and Cellular Biology of Cancer (IBMCC), University-CSIC, Salamanca

Background/Objectives: Hypoxia is common in solid tumour microenvironments and has been associated with radiotherapy resistance and poor clinical outcomes. Replicating hypoxic conditions in vitro requires incubation at 1% O2, 5% CO2 and 94% N2. This nitrogen-induced hypoxia is costly and time-consuming since it needs 24 hours to establish hypoxia. An alternative technique to replicate hypoxic conditions is the use of mimetics like deferoxamine (DFO). This molecule is an iron chelating agent that facilitates the accumulation of hypoxia-inducible factors and has been shown to induce apoptosis in breast tumor cell lines1.

Methods: MCF7 (breast), VCAP (prostate), CAL33 (head and neck) and OVCAR-8 (ovarian) cancer cell lines were used to test the effect of DFO on proliferation using MTT and annexin-V/propidium iodide assays. DNA damage, specifically double strand break (DSB) formation, was tested by γH2AX foci quantification via immunofluorescence assays.

Results: DFO inhibited cell proliferation and apoptosis in a dose- and time-dependent manner. These effects were more marked than the one achieved through nitrogen-induced hypoxia. Additionally, DFO induces DNA damage through DSB formation.

Conclusion: Although DFO is usually used as a hypoxia-mimetic agent because it is cheaper and less time-consuming than nitrogen-induced hypoxia, our results show that it decreases cell proliferation and induces DNA damage through DSB formation. Therefore, its antitumoral effect should be further explored.

Grants: Study was financed by Gerencia Regional de Salud, JCyL (GRS2171/A/2020)

1.

Lynn, J. V. et al. The Role of Deferoxamine in Irradiated Breast Reconstruction: A Study of Oncologic Safety. Plast. Reconstr. Surg. 143, 1666–1676 (2019).

Conflict of Interest: None declared

P01.002.B Mapping of Splicing Regulatory Elements-rich intervals and identification of spliceogenic variants in ATM exon 7

Inés Llinares-Burguet 1, Lara Sanoguera-Miralles1, Elena Bueno-Martínez1, Alicia García-Álvarez1, Eladio A. Velasco-Sampedro1 1Instituto de Biomedicina y Genética Molecular de Valladolid (IBGM), Consejo Superior de Investigaciones Científicas – Universidad de Valladolid (CSIC-UVa), Splicing and Genetic Susceptibility to Cancer Laboratory, Valladolid, Spain

Background/Objectives: Alternative splicing regulates gene expression patterns and is controlled by splicing regulatory elements (SRE). Mutations in SREs might affect splicing and be involved in disease susceptibility. Our purpose was to study the alternatively spliced exon 7 of the breast cancer susceptibility gene ATM.

Methods: A minigene with exons 4 to 9 of ATM (MG_ATM_4-9) was used in this work. The enhancer/silencer profile in ATM exon 7 was bioinformatically analysed by HexPlorer to identify the potential regions to study. Selected sequences were deleted in MG_ATM_4-9 by site-directed mutagenesis. In the region with more impact on exon 7 inclusion, we introduced 3 internal overlapping microdeletions. Additionally, we tested all possible variants localised in critical SRE intervals and variants with HexPlorer score below -40 were selected. Thus, 19 variants were introduced into the minigene and functionally tested.

Results: We identified two minimal regions (12/13-nt) involved in exon recognition, located in the 3’-end exon [△(E7): 50-75%]. Of the 19 variants analysed, seventeen (89%) impaired splicing, seven of which had strong impact on splicing, producing exon 7 skipping (59-69%) and <30% of the minigene full-length transcript.

Conclusion: The functional SRE mapping by exonic microdeletions was a useful approach to identify enhancer-rich sequences and SRE variants that impair splicing. The identification of spliceogenic variants is a helpful tool in the genetic counselling consultation, facilitating the early detection and diagnostic of diseases.

Grants: Predoctoral fellowship from the Junta de Castilla y León (2022-2025); ISCIII (PI20/00225 and PI23/00047).

Conflict of Interest: None declared

P01.003.C Rare Germline Variants in glioma: A genomic analysis of 125 individuals from Northern Sweden

Adam Rosenbaum 1, Anna Dahlin1, Carl Wibom1, Beatrice Melin1 1Umeå universitet, Department of Diagnostics and Intervention, Umeå, Sweden

Background/Objectives: The etiology of glioma, the most common malignant CNS tumor, remains inadequately understood. Although germline predisposition, including common and rare variants, have been studied, the role of rare germline variants to glioma predisposition remains insufficiently explored.

Methods: We conducted whole genome sequencing on germline samples from 125 individuals from Northern Sweden, diagnosed with various subtypes of glioma. Of these, 46 were diagnosed before 40 years of age, and 12 familial gliomas from 5 families. We studied rare variants in established cancer predisposition genes, as well as a broader investigation of other genes with rare likely pathogenic variants.

Results: Our study reveals 20 rare coding variants in 18 genes, including TP53. Several are likely pathogenic and reside within known cancer predisposition genes, suggesting a link to glioma development. We identified rare variants in genes not previously associated with glioma, providing possible new insights into the etiology of glioma. Comparing the frequency of rare coding mutation among our cases and 300 individuals of similar lineage 7 genes have a significantly increased burden of rare coding variants. These genes are awaiting validation.

Conclusion: Our findings show that the germline genetic predisposition to glioma still holds some explanatory potential to the development of the disease. Continuing studying this aspect of predisposition may unlock new understanding of glioma development.

Grants: Swedish Cancer Society (CAN2018/390 to BM)

Swedish Research Council (2019-01566 to BM)

Umeå University Hospital Grant (7003839 to BM)

Northern Sweden Cancer Foundation (AMP 23-1141 to AR)

Conflict of Interest: None declared

P01.007.C Large genomic rearrangement: tandem duplication and triplication in BRCA1 gene causative for hereditary breast and ovarian cancer

Bernardus Aldrige Allister 1, Jonathan Lühmann1, Lena Wendeburg1, Tim Ripperger1, Bernd Auber1, Frank Dechend2, Carmela Beger3, Stefanie Tölle3, Julia von Ehr4, Nataliya Di Donato1, Doris Steinemann1 1Hannover medical school (MHH), Department of Human Genetics, Hannover, Germany; 2MVZ Reproduction Medicine and Human Genetics, Hildesheim, Germany; 3MVZ Labor Krone GbR, Bad Salzuflen / Bielefeld, Germany; 4Frauenärzte am Schloss, Wolfenbüttel, Germany

Background/Objectives: Large genomic rearrangements (LGRs) include copy number variations like duplications or triplications of coding or non-coding genomic regions within the human genome. Here, we report on two LGRs in two families with the suspicion of hereditary breast and/or ovarian cancer (HBOC) syndrome, a pathogenic BRCA1 tandem duplication targeting exon 18-19 and a for the first time a pathogenic BRCA1 tandem triplication of exon 2.

Methods: MLPA, Optical Genome Mapping (OGM), cDNA analysis and Sanger sequencing have been performed to identify these rearrangements and to characterize their localization and orientation as well as to predict their pathogenicity for HBOC development.

Results: We show that the duplication of exon 18-19 in BRCA1, is a tandem duplication: ogm[GRCh38] dup(17)(q21.31q21.31)(43057052_43063373). Validation by sanger sequencing of the cDNA shows that this tandem duplication of exon 18-19 generate a premature termination codon at the second codon of the duplicated exon 18. In the second index patient, four copies of the BRCA1 promotor region, exon 1a,1b and exon 2 were detected via MLPA and OGM enabled us to resolve this LGR as a BRCA1 exon 2 tandem triplication: ogm[GRCh38] trip(17)(q21.31q21.31)(43117155_43124115). cDNA analysis shows that this LGR causes an inclusion of a portion of intron 2 sequence and provokes a premature termination codon exactly at the junction between exon 2 and the intronic sequence of intron 2.

Conclusion: Due to a predicted premature termination codon we classify both LGRs as pathogenic variants. This signifies that LGRs such as tandem duplications and triplications can be causative for HBOC.

Grants:

Conflict of Interest: None declared

P01.008.D Atypical cancer risk profile in carriers of Italian founder BRCA1 variant p.His1673del: implications for classification and clinical management

Giovanni Innella 1;2, Cristina Fortuno3, Laura Caleca4, Bing-Jian Feng5, Courtney Carroll5, Michael T. Parsons3, Sara Miccoli2, Marco Montagna6, Daniele Calistri7, Laura Cortesi8, Barbara Pasini9, Siranoush Manoukian10, Daniela Giachino11, Laura Matricardi6, Maria Cristina Foti6, Valentina Zampiga7, Claudia Piombino8, Elena Barbieri8, Francesca Vignolo9, Jacopo Azzolini10, Rita Danesi12, Valentina Arcangeli12, Sandrine Caputo13, Nadia Boutry-Kryza14, Vincent Goussot15, Susan Hiraki16, Marcy Richardson17, Simona Ferrari2, Paolo Radice4, Amanda B. Spurdle3, Daniela Turchetti1;2 1Università di Bologna, Dipartimento di Scienze Mediche e Chirurgiche, Bologna, Italy; 22.IRCCS Azienda Ospedaliero-Universitaria di Bologna, Medical Genetics Unit, Bologna, Italy; 3QIMR Berghofer Medical Research Institute, Population Health, Brisbane, Australia; 4Fondazione IRCCS Istituto Nazionale dei Tumori, Unit of Predictive Medicine: Molecular Bases of Genetic Risk, Department of Experimental Oncology, Milano, Italy; 5University of Utah, Salt Lake City, United States; 6Veneto Institute of Oncology IOV - IRCCS, Immunology and Molecular Oncology Unit, Padova, Italy; 7IRCCS Istituto Romagnolo per lo Studio dei Tumori “Dino Amadori” IRST, SC Laboratorio di Bioscienze, Meldola, Italy; 8Centro Oncologico Modenese, Azienda Ospedaliero-Universitaria Policlinico di Modena, Dipartimento di Oncologia ed Ematologia, Modena, Italy; 9Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, SC Genetica Medica U, Torino, Italy; 10Fondazione IRCCS Istituto Nazionale dei Tumori, Unit of Medical Genetics, Department of Medical Oncology and Hematology, Milano, Italy; 11Azienda Ospedaliero-Universitaria San Luigi Gonzaga, Regione Gonzole, Counselling Genetico, Orbassano, Italy; 12IRCCS Istituto Romagnolo per lo Studio dei Tumori “Dino Amadori” IRST, SC Epidemiologia Clinica e Sperimentale, Meldola, Italy; 13, Institut Curie, Paris, France and Paris Sciences Lettres Research University, Department of Genetics, Paris, France; 14Hospices Civils de Lyon, Service de génétique, Lyon, France; 15Centre de Lutte Contre le Cancer Georges François Leclerc, Département de Biologie et Pathologie des Tumeurs, Dijon, France; 16GeneDx, Gaithersburg, United States; 17Ambry Genetics, Aliso Viejo, United States

Background/Objectives: BRCA1:c.5017_5019del(p.His1673del) is a founder variant relatively frequent in Northern Italy. Despite previous suggestion of pathogenicity, variant classification in public databases is still conflicting, needing additional evidence.

Methods: Maximum likelihood penetrance of breast/ovarian and other cancer types was estimated using full pedigree data from 53 informative Italian families. The effect of the variant on BRCA1-ABRAXAS1 interaction was assessed using a GFP-fragment reassembly-based PPI assay. Results were combined with additional data from multiple sources to classify the variant according to ACMG/AMP classification rules specified for BRCA1/2.

Results: Variant-carriers displayed increased risk for ovarian cancer (HR = 33.0, 95%CI = 7.0-155.0; cumulative risk at age 70 = 27.6%, 95%CI = 12.6-40.0%) but not for breast cancer (HR = 0.7, 95%CI = 0.2-2.2). An increased risk of uterine cancer (HR = 8.0, 95%CI = 1.03-61.6) emerged, warranting further evaluation. Likelihood ratio in favor of pathogenicity was 98898642.82 under assumption of standard BRCA1 breast and ovarian penetrance, and 104240832.84 after excluding breast cancer diagnoses (based on penetrance results). Functional analysis demonstrated that the variant abrogates the BRCA1-ABRAXAS1 binding, supporting the PS3 code assignment within the ACMG/AMP rule-based model. Collectively, these findings allowed to classify the variant as pathogenic.

Conclusion: Pathogenicity of BRCA1:c.5017_5019del(p.His1673del) has been confirmed; however, breast cancer risk in Italian families is not increased, unlike in families from other countries and in carriers of most BRCA1 pathogenic variants. Haplotype analysis is underway to explore the hypothesis of potential in-cis modifiers. Nevertheless, the knowledge of atypical risk profiles for this and other variants will pave the way for personalized management based on specific genotype.

Grants:

Conflict of Interest: Giovanni Innella: None declared, Cristina Fortuno National Breast Cancer Foundation, Australia (IIRS-21-102), Laura Caleca Italian Association for Cancer Research (AIRC; IG22093), Bing-Jian Feng: None declared, Courtney Carroll: None declared, Michael T. Parsons National Institutes of Health grant U24 5U24CA258058-02, Sara Miccoli: None declared, Marco Montagna: None declared, Daniele Calistri: None declared, Laura Cortesi: None declared, Barbara Pasini: None declared, Siranoush Manoukian: None declared, Daniela Giachino: None declared, Laura Matricardi: None declared, Maria Cristina Foti: None declared, Valentina Zampiga: None declared, Claudia Piombino: None declared, Elena Barbieri: None declared, Francesca Vignolo: None declared, Jacopo Azzolini: None declared, Rita Danesi: None declared, Valentina Arcangeli: None declared, Sandrine Caputo: None declared, Nadia Boutry-Kryza: None declared, Vincent Goussot: None declared, Susan Hiraki: None declared, Marcy Richardson: None declared, Simona Ferrari: None declared, Paolo Radice Italian Association for Cancer Research (AIRC; IG22093), Amanda B. Spurdle NHMRC Investigator Fellowship (APP177524), Daniela Turchetti: None declared

P01.009.A Further elucidating the genetic landscape of glioma predisposition in a European familial glioma cohort

Frank Brand 1, Amir H. Akbarzadeh1, Christine A. M. Weber1, Lily S. Rose1, Robert Geffers2, Gunnar Schmidt1, Bernd Auber1, Michael Friese3, Mareike Müller4, Michael Lalk5, Isabel Eckert6, Arya Nabavi5, Paul Kremer7, Amir Samii8, Guido Reifenberger9;10, Joachim K. Krauss11, Bettina Wiese6;11, Christian Hartmann12, Ruthild G. Weber1 1Hannover Medical School, Department of Human Genetics, Hannover, Germany; 2Helmholtz Centre for Infection Research, Genome Analytics Research Group, Braunschweig, Germany; 3Asklepios Klinik Nord - Heidberg, Department of Pathology and Neuropathology, Hamburg, Germany; 4Heinrich Heine University, Medical Faculty, Department of Neurosurgery, Düsseldorf, Germany; 5KRH Klinikum Nordstadt, Department of Neurosurgery, Hannover, Germany; 6Diakovere Krankenhaus gGmbH, Henriettenstift, Department of Neurology, Hannover, Germany; 7Asklepios Klinik Nord - Heidberg, Department of Neurosurgery, Hamburg, Germany; 8International Neuroscience Institute, Department of Neurosurgery, Hannover, Germany; 9Heinrich Heine University, Medical Faculty, Institute of Neuropathology, Düsseldorf, Germany; 10German Cancer Consortium (DKTK), Partner Site Essen/Düsseldorf and German Cancer Research Center (DKFZ), Heidelberg, Germany; 11Hannover Medical School, Department of Neurosurgery, Hannover, Germany; 12Hannover Medical School, Institute of Pathology, Department of Neuropathology, Hannover, Germany

Background/Objectives: Familial occurrence of glioma, the most common type of malignant brain tumor, is observed in about 5% of cases. Studies on the genetic landscape of glioma predisposition are still scarce.

Methods: Leukocyte DNA of 122 glioma patients from 115 tumor families with at least one glioma patient each were analyzed by whole-exome sequencing. Data were analyzed using two approaches: (1) variants in established cancer predisposition genes (CPGs) or suspected glioma risk genes (n = 154) were extracted and classified, (2) the frequency of rare (MAF < 0.01%) or deleterious variants in all genes in the glioma cohort was compared with that in a control cohort (n = 257 families). Exome data of >70 additional patients are pending and will be included in our analysis.

Results: Both approaches associated BRCA2 variants, including the pathogenic variants c.316+5G > C, p.(K944*), p.(I1470Kfs*11), most strongly with familial glioma. BRCA2 variants were significantly more frequent in the glioma than in the control cohort (P = 0.0088). In addition, rare deleterious variants in APC, ATM, and EGFR were recurrently observed in the glioma cohort. In agreement with Choi et al., Sci. Adv., 2023, our familial glioma cases carried rare deleterious variants in known CPGs, e.g. ATM, PMS2, and POLE, and novel CPGs, e.g. SLC4A7 and WDR7. Furthermore, we identified 31 genes, not previously associated with cancer predisposition, that were recurrently affected in the glioma but not at all in the control cohort.

Conclusion: Our study on a large European familial glioma cohort implicates known CPGs, particularly BRCA2 and ATM, and novel CPGs in glioma risk.

Conflict of Interest: None declared

P01.010.B Analysis of aberrant splicing in capture RNA-seq data as a supplement to DNA germline testing to increase diagnostic yield

Florentine Scharf1, Thomas Keßler1, Evgenia Vibe 1, Oliver Klaas1, Jonas Ingermann1, Caroline Heintz1, Anna Benet-Pages1;2, Sabrina Angerbauer1, Martin Wendlandt1, Tobias Wohlfrom1, Verena Steinke-Lange1;3, Andreas Laner1, Ariane Hallermayr1;3, Julia Romic-Pickl1;3, Morghan Lucas1;3, Elke Holinski-Feder1;3 1MGZ – Medizinisch Genetisches Zentrum, Munich, Germany; 2Institute of Neurogenomics, Helmholtz Research Center, München, Germany; 3Medizinische Klinik und Poliklinik IV, Campus Innenstadt, Klinikum der Universität München

Background/Objectives: Hereditary tumor syndromes comprise 5-10% of cancer cases, necessitating accurate identification of causal genetic variants for effective patient management. The diagnostic yield of whole-exome sequencing (WES), the gold standard for molecular diagnostics, ranges from 15-25% in these syndromes. High-throughput functional studies, such as RNA sequencing (RNA-seq), play a crucial role in reclassifying variants of uncertain significance (VUS) and unveiling pathomechanisms like aberrant splicing, particularly when initial variant detection fails.

Methods: We developed a cost-efficient, high-throughput RNA-seq approach to analyze RNA phenotypes where we complement polyA mRNA or hexamer capture with enrichment of 49 cancer-associated genes from PAXgene-derived RNA samples.

Results: We achieved ultra-high coverage sequencing data of ~3,500X mean target coverage and, on average, 80% of exons covered with >50 read depth using hexamer capture and target enrichment. In almost 80% of positive controls for aberrant splicing, we detected a difference of >20% in the PSI (percent-spliced in) score compared to negative controls.

Conclusion: Our workflow provides high-quality RNA-seq data, which allows the assessment of splicing events. Our data on the comparisons between positive and negative controls substantiate the possibility of an automated high throughput pipeline. This work represents the basis for implementing targeted RNA-seq in cancer diagnostics, in which we want to establish the parallel analysis of WES and RNA-seq to increase the diagnostic yield and turnaround time for patients with hereditary tumor syndromes.

Grants: N/A

Conflict of Interest: None declared

P01.011.C Identification of shared genetic variants among different cancers and between adenomyosis and cancer utilizing members of the same family

Sevcan Aydın 1, nura fitnat topbas selcuki2, pinar yalcin bahat3, engin oral4, Feyza Tuncer5 1Istanbul University, Graduate School of Health Sciences, Istanbul, Türkyie; 2University of Health Sciences Turkey, Istanbul Sisli Hamidiye Etfal Training and Research Hospital, Obstetrics and Gynecology, Istanbul, Türkyie; 3University of Health Sciences Turkey, Istanbul Kanuni Sultan Suleyman Training and Research Hospital, Department, Obstetrics and Gynecology, Istanbul, Türkyie; 4Biruni University Faculty of Medicine, Obstetrics and Gynecology, Istanbul, Türkyie; 5Istanbul University, Aziz Sancar Institute of Experimental Medicine, Genetics, Istanbul, Türkyie

Background/Objectıves: Adenomyosis is a benign uterine condition characterized by the localization of endometrial-like tissue in myometrium. Its pathogenesis remains elusive, but it carries cancer-like characteristics. We aimed to identify shared genetic variants both between different cancers and adenomyosis and cancer, utilizing a family having women affected by both conditions.

Methods: Five women from the same family were subjected to gynecological examinations via transvaginal ultrasonography, amongst two receieved pathologically confirmed diagnosis of ovarian mucinous adenocarcinoma and clear cell renal cell carcinoma (ccRCC). Whole exome sequencing was performed on all women utilizing Illumina NextSeq550. Bioinformatic analyses were performed on Genomize SEQ and Pairend platforms, MAF < %1 was applied to identify rare and novel variants. Cases with cancer versus all cases were evaluated in parallel, for which one member was utilized as a control, who manifested neither of the conditions.

Result: Pathological evaluations excluded adenomyosis in the case diagnosed with ovarian mucinous adenocarcinoma, while the case with ccRCC received adenomyosis diagnosis. A novel genetic variant in NTN1 gene was identified across all cases, in addition to rare variants in 10 genes shared among cases with cancers.

Conclusıon: NTN1 gene might be one of the many links between the pathogenesis of cancer and adenomyosis, fitting in with its attributed roles in cell migration and angiogenesis. The impact of the novel variant in NTN1 merits clarification functionally. Further studies are in need to elucidate the diversifying mechanisms among two similar conditions evolving towards either malignity or benignity.

Grant Reference:Istanbul University Scientific Research Projects Coordination Unit(TSA-2023-38950)

Conflict of Interest: None declared

P01.012.D Reproductive factors and sex hormones levels on differentiated thyroid cancer risk: A Mendelian Randomization study

See Hyun PARK 1;2, Mojgan Karimi2, Cloe Domenighetti2, Thérèse Truong2 1Paris Saclay Universite, Gif-sur-Yvette, France; 2INSERM, Exposome and Heredity, Villejuif

Consortium: EPITHYR consortium, and The European Prospective Investigation into Cancer and Nutrition (EPIC-Europe)

Background: Differentiated thyroid carcinoma (DTC) is the most common type of thyroid cancer, occurring three times more frequently in women than in men. However, the underlying biological mechanisms driving this sex-specific discrepancy remain poorly understood. To analyze the causal role of sex hormones and reproductive factors in the risk of DTC, we implemented a two-sample Mendelian Randomization (MR) analysis using genome-wide association studies (GWAS) summary statistics.

Methods: GWAS on DTC were derived from a meta-analysis of 6 studies including 7,705 cases and 963,612 controls of European population, while GWAS summary statistics on sex hormones, reproductive factors, and gynecological factors related to hysterectomy were retrieved from publicly available literature. We used the inverse-variance weighted method to estimate odds ratio, with additional multiple sensitivity analyses to ensure the suitability of the MR analysis, and conducted multivariable MR to account for potential confounding variables.

Results: We showed that endometrial cancer was associated with DTC (OR = 1.15, p = 9 × 10-3). We also observed an association between SHBG levels and increased risk of DTC, however this association lost significance upon adjustment for obesity-related factors. Putative causal associations was observed with uterine fibroids; nonetheless, this association was not supported by additional sensitivity analyses. No significant associations were found for levels of sex hormones, age at menopause, menarche and first birth, nor with endometriosis.

Conclusion: Using the largest GWAS on DTC to date, our findings do not support a significant influence of sex hormones and reproductive factors in the observed differences in DTC risk between women and men.

Grants: Funded by doctoral school of Université Paris-Saclay

Conflict of Interest: None declared

P01.013.A Evolution of genomic profiles in primary and recurrent astrocytic gliomas

Libuse Lizcova 1, Halka Lhotska1, Karolina Janeckova1, Lucie Hodanova1, Karla Svobodova1, Hana Cechova2, Tatiana Aghova1, Sarka Ransdorfova2, Lenka Pavlistova1, Filip Kramar3, David Netuka3, Zuzana Zemanova1 1General University Hospital and First Faculty of Medicine, Charles University in Prague, Center of Oncocytogenomics,Institute of Medical Biochemistry and Laboratory Diagnostics, Prague, Czech Republic; 2Institute of Hematology and Blood Transfusion, Prague, Czech Republic; 3First Faculty of Medicine of Charles University and Military University Hospital Prague, Department of Neurosurgery and Neurooncology, Prague

Background/Objectives: Astrocytic gliomas, including grades 2-4 astrocytoma and grade 4 glioblastoma, are characterized by diverse biological behaviors and recurrent lesions. During disease progression, these tumors undergo genomic evolution with newly acquired genetic properties. However, the mechanisms and evolutionary dynamics underlying tumor progression and relapse remain poorly understood.

Methods: Genomic profiles of 35 paired glioma samples (primary and recurrent; 15x astrocytoma, 20x glioblastoma) were analyzed using combination of cytogenomic methods: I-FISH (Abbott Molecular, MetaSystems), aCGH/SNP (Agilent), MLPA, MS-MLPA (MRC-Holland) and targeted NGS panel (Invitae).

Results: Primary tumors displayed common aberrations like IDH1/IDH2 and TERT mutations, CNAs of chromosome 7, 10, and CDKN2A/2B and EGFR genes, persisting in recurrent lesions. All but two patients experienced recurrences with newly acquired genetic/epigenetic changes with a high frequency of CNAs leading to complex rearrangements. Divergent clonal evolution was observed in 22 cases, while 11 cases displayed linear evolution. Aberrations of chromosomal regions 4p, 6p, 8q, 9q, 11p and 11q were recurrently identified in recurrences. cnLOH was proved in 22 cases, mainly on 7p and 17p. Disease progression occurred in 28 patients.

Conclusions: This study highlights heterogeneity in tumor evolution driven by genomic/microenvironmental imbalances or treatment. Recurrence may arise from major tumor clone or multiple subclones within the primary tumor. Cytogenomic analyses of recurrent tissues contribute to understanding these processes and identification of alterations associated with glioma progression. These biomarkers could subsequently serve as resource for precision oncology targeting cancer dynamics in astrocytic gliomas.

Grants: MH CZ AZV-NU21-04-00100, MH CZ-DRO-0064165 and GAUK 159020.

Conflict of Interest: None declared

P01.014.B PAX5 alterations in a consecutive childhood B-ALL cohort treated on ALL IC-BFM 2009 protocol

Klementina Črepinšek 1;2, Janez Jazbec2;3, Marko Kavčič2;3, Tomaž Prelog3, Tine Tesovnik1;2, Barbara Jenko Bizjan1;2, Robert Sket1;2, Jernej Kovač1;2, Marusa Debeljak1;2 1University Children’s Hospital, UMC Ljubljana, Clinical Institute for Special Laboratory Diagnostics, Ljubljana, Slovenia; 2University of Ljubljana, Faculty of Medicine, Ljubljana; 3University Children’s Hospital, UMC Ljubljana, Department of Oncology and Haematology, Ljubljana

Background/Objectives: In this study, we aimed to identify patients within our B-ALL cohort with altered PAX5. Our objective was to characterize the types of genetic changes, determine their origin (somatic/germline), and analyze the clinical outcomes associated with them.

Methods: A consecutive cohort of 99 patients with B-ALL treated at the Children’s Hospital of the UMC Ljubljana according to the ALL IC-BFM 2009 protocol was included in our study. We used RNA sequencing data for gene expression analysis, fusion gene detection and variant identification, multiplex-ligation dependent probe amplification for copy number variation assessment, and Sanger sequencing to detect germline variants.

Results: PAX5 was impacted in a 33.3% of our patients, with the genetic alterations ranging from CNVs and rearrangements to SNVs. The most common were CNVs, which were found in 33.7% of patients, followed by point mutations in 5.2% and gene rearrangements in 4.1%. We identified 8 patients with a PAX5-associated genetic subtypes that were previously classified as “B-other”, and they showed intermediate outcomes. We showed a trend of poorer survival in hyperdiploid cases carrying duplications in PAX5 compared to other hyperdiploid cases. We also report an interesting case of a patient with PAX5::FKBP15 and a pathogenic variant in PTPN11 who underwent an early relapse with a monocytic switch.

Conclusion: In conclusion, this study provides valuable insights into the presence, frequency, and prognostic significance of diverse PAX5 alterations in B-ALL patients, highlighting the complexity of genetic factors and their impact on patient outcomes.

Grants: Young Research Fellowship SRA#54654, UMC-tertiary grants: TP20230039

Conflict of Interest: None declared

P01.015.C Rare mutations in FH and POLE genes in a patient with Ewing sarcoma and familial cancer burden

Dimitar Bakalov 1, Svilen Maslyankov2, Kalina Belemezova3, Radka Tafradjiiska-Hadjiolova1, Zafer Sabit1, Ivanka Dimova4 1Medical University of Sofia, Department of Physiology and Pathophysiology, Sofia, Bulgaria; 2Medical University of Sofia, Department of Surgery, Sofia, Bulgaria; 3Medical University of Sofia, Department of Medical Biology, Sofia, Bulgaria; 4Medical University of Sofia, Department of Medical Genetics, Sofia, Bulgaria

Background/objectives: Ewing sarcoma is a rare and aggressive form of bone and soft tissue cancer, predominantly affecting young individuals. We explore the underlying genetic factors contributing to Ewing sarcoma in a 22-year-old patient, having familial cancer burden (colon, kidney, breast, bladder, melanoma).

Methods: Whole exome sequencing was performed on genomic DNA from the affected individual. Comprehensive bioinformatic analyses were employed to prioritize and validate variants, with a particular focus on genes implicated in cancer susceptibility.

Results: The analysis revealed two very rare heterozygous missense variants of unknown significance: c.809 A > G (p.Tyr270Cys) in the FH gene (frequency of 3e-5) and c.1015 G > A (p.Asp339Asn) in POLE gene (frequency of 8e-5) in the patient’s germline. FH encodes fumarate hydratase, a key enzyme in the tricarboxylic acid cycle, which is associated with autosomal dominant “Leiomyomatosis and renal cancer” phenotype. POLE is essential for DNA replication and repair, and is associated with autosomal dominant “Colorectal cancer, succeptibility to, 12” phenotype.

Conclusion: This study contributes to the growing body of knowledge surrounding the genetic landscape of Ewing sarcoma, highlighting the role of FH and POLE gene variants. Additionally, the severe family history of colon, urothelial, breast and skin cancers in first- and second-degree relatives raises intriguing questions about shared genetic predisposition. Further investigations into the potential synergistic effects of these variants and their implications for familial cancer risk are warranted. This case underscores the importance of genetic counseling in individuals with Ewing sarcoma and multidisciplinary approach to personalized cancer care.

Grant: Project № BG-RRP-2.004-0004-C01

Conflict of Interest: None declared

P01.016.D Liquid biopsy integrating machine learning for prostate cancer detection

Ondrej Pös 1;2, Zuzana Hanzlikova2;3, Jaroslav Budiš1;2;4, Jakub Styk1;2, Matej Hrnčiar2, Werner Krampl1;2;5, Tomáš Sládeček1;2, Jozef Sitarcik1;2, Pavol Misenko2, Silvia Bokorova1;2, Diana Rusnakova1;2, Lydia Lukyova1;5, Monika Kubanova1, Terezia Duranova1, Tatiana Sedlackova1;2, Tomas Szemes1;2;5 1Comenius University Science Park, Bratislava, Slovakia; 2Geneton Ltd., Bratislava, Slovakia; 3Faculty of Informatics and Information Technologies, Slovak University of Technology, Bratislava, Slovakia; 4Slovak Center of Scientific and Technical Information, Bratislava, Slovakia; 5Faculty of Natural Sciences, Comenius University, Department of Molecular Biology, Bratislava, Slovakia

Background/Objectives: Early-stage cancer manifests with minimal or no noticeable symptoms, leading to a diagnostic delay and subsequent less effective treatment. Since analysis of cell-free DNA (cfDNA) may serve to identify early neoplastic changes, liquid biopsy-based tests hold potential for non-invasive cancer screening.

Methods: The plasma of 60 prostate cancer patients and 369 control individuals were collected to analyze cfDNA by low-coverage whole-genome next-generation sequencing. Data were processed using an in-house bioinformatics pipeline to detect genetic variability and characterize qualitative and quantitative sequencing metrics. A total of 379 samples (49 patients, 330 controls) were used to train the model from decision trees using gradient boosting to facilitate prostate cancer prediction. Subsequently, a testing set of 50 samples (11 patients, 39 control) was used to assess the accuracy of the model.

Results: The robust combination and evaluation of 671 attributes, including genomic variability and sequencing metrics, by ensemble learning model, have shown a sensitivity of 81.8% and specificity of 100.0% on the testing dataset. The ROC AUC of 97.4% suggests a high prediction capability of the test.

Conclusion: Here, we emphasize the decent potential of liquid biopsy test enhanced by artificial intelligence to evaluate an extensive set of cfDNA sequencing metrics and genomic attributes for non-invasive prostate cancer screening.

Grants: The work was supported by the OPII project ITMS: 313010Q927 (GenoScan LBquant), co-financed by ERDF. Support was also provided by Horizon Europe Framework Programme Grant agreement ID: 101087124 (ADDIT-CE) and by Slovak Research and Development Agency grants APVV-21-0296 (INCAM) and APVV-20-0472 (Sepmin).

Conflict of Interest: Ondrej Pös The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Zuzana Hanzlikova The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Jaroslav Budiš The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Jakub Styk The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Matej Hrnčiar The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Werner Krampl The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Tomáš Sládeček The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Jozef Sitarcik The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Pavol Misenko The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Silvia Bokorova The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Diana Rusnakova The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Lydia Lukyova: None declared, Monika Kubanova: None declared, Terezia Duranova: None declared, Tatiana Sedlackova The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company., Tomas Szemes The author is an employee of Geneton Ltd. and is involved in numerous research and development efforts to adapt novel approaches to liquid biopsy screening applications. However, the employee does not hold any financial interest in the company.

P01.017.A Development and validation of an expanded comprehensive genomic profiling assay with enhanced variant sensitivity for tumor biopsies

Stephanie Constantinou 1, Alexia Eliades1, Kyriakos Tsangaras1, Chrysa Soteriou1, chrystalla lazarou1, Achilleas Achilleos1, charalambos loizides1, Christos Lemesios1, Chrystalla Havadjia1, sarah barbour1, aris pallaris1, chrysovalando soteriou1, Louisa Constantinou1, Haris Kkoufou1, Michalis Spyrou1, antonis antoniou1, Antonia Matsentidou1, Melina Vaki1, george manoli1, Christos Prokopi1, Styliana Georgiou1, Elena Kypri1, Marios Ioannides1, George Koumbaris1, Philippos Patsalis1;2 1Medicover Genetics, Nicosia, Cyprus; 2University of Nicosia Medical School, Department of Basic and Clinical Sciences, Nicosia, Cyprus

Background/Objectives: Comprehensive genomic profiling using next-generation sequencing (NGS) has become increasingly important in the classification and management of cancer, enabling a growing number of patients to benefit from targeted therapies. Such approved therapies include ones developed for less prevalent gene alterations, thus emphasising the need for assessing a broader panel of genes for multiple alteration classes with an enhanced sensitivity. Herein, we describe the development of an expanded 392-gene panel, offering high analytical performance.

Methods: DNA isolated from a set of formalin-fixed, paraffin-embedded (FFPE) tissue samples comprising reference materials, non-malignant and tumor samples was subjected to library preparation and hybrid capture enrichment with our expanded 392-gene panel. Enriched libraries were subsequently sequenced by NGS on a NovaSeq platform and data was analysed using proprietary bioinformatic pipelines.

Results: A set of FFPE samples comprising benign, malignant and reference material samples, was used to evaluate the assay’s analytical performance. The assay demonstrated high sensitivity and specificity for all classes of genomic alterations, including single nucleotide variants (SNVs), small insertions and deletions (Indels), copy number alterations (CNAs), translocations, as well as the immuno-oncology biomarkers, microsatellite instability (MSI) and tumor mutational burden (TMB). Notably, the developed assay can detect mutations down to 1% variant allele frequency (VAF).

Conclusion: Validation results demonstrate the development of a tissue-based NGS assay for the assessment of an expanded panel of genomic alterations and therapy-associated biomarkers that can detect less prevalent variants with enhanced sensitivity.

Conflict of Interest: Stephanie Constantinou Author employed by Medicover Genetics, Alexia Eliades Author employed by Medicover Genetics, Kyriakos Tsangaras Author employed by Medicover Genetics, Chrysa Soteriou Author employed by Medicover Genetics, chrystalla lazarou Author employed by Medicover Genetics, Achilleas Achilleos Author employed by Medicover Genetics, charalambos loizides Author employed by Medicover Genetics, Christos Lemesios Author employed by Medicover Genetics, Chrystalla Havadjia Author employed by Medicover Genetics, sarah barbour Author employed by Medicover Genetics, aris pallaris Author employed by Medicover Genetics, chrysovalando soteriou Author employed by Medicover Genetics, Louisa Constantinou Author employed by Medicover Genetics, Haris Kkoufou Author employed by Medicover Genetics, Michalis Spyrou Author employed by Medicover Genetics, antonis antoniou Author employed by Medicover Genetics, Antonia Matsentidou Author employed by Medicover Genetics, Melina Vaki Author employed by Medicover Genetics, george manoli Author employed by Medicover Genetics, Christos Prokopi Author employed by Medicover Genetics, Styliana Georgiou Author employed by Medicover Genetics, Elena Kypri Author employed by Medicover Genetics, Marios Ioannides Author employed by Medicover Genetics, George Koumbaris Author employed by Medicover Genetics, Philippos Patsalis Author employed by Medicover Genetics

P01.019.C Increased prevalence of pathogenic and likely pathogenic CHEK2 variants in the Balearic Islands Hereditary Cancer cohorts.

Maria Antònia Caro-Miró 1, Catalina Lladó-Sampol2, Antònia Perelló-Martorell2, Evelin Horvath2, Paloma de la Torre-Rubio3, DAMIAN HEINE SUÑER1, Victor Asensio-Landa1, Laura Torres-Juan1, María Carmen Prado-Farnos1, Susana Renee Avella-Klaassen1, Iciar Martínez1, Jesús Alarcón Company2, Antonia Obrador-Hevia1 1Hospital Universitari Son Espases, Molecular Diagnosis and Clinical Genetics Unit, Palma, Spain; 2Hospital Universitari Son Espases, Oncology, Palma, Spain; 3Hospital Universitari Son Espases, Digestology, Palma, Spain

Background/Objectives: CHEK2 has been identified as an intermediate-risk gene associated with breast, prostate, and colon cancer (OMIM: 609265).

In this study, we examined the frequency and mutational spectrum of CHEK2 variants within the Balearic Islands’ hereditary cancer (HC) cohort, comparing it to the Catalonian population databases in order to investigate potential founder mutations.

Methods: The research assessed the prevalence of pathogenic/likely pathogenic (P/LP) CHEK2 variants and included two Balearic Island cohorts: 1559 patients from the HC cohort sequenced by the TruSight Hereditary Cancer panel (Illumina®) between 2016 and 2022, and 3352 non-HC patients sequenced via Whole Exome Sequencing (WES) (Illumina®). Frequencies from the genetically closest population, Catalonia, were used for comparison.

Results:

Group

Patients

Patients (%) with P/LP variants in CHEK2*

Breast, ovarian and prostate (BOP) cancer

1101

24 (2.2%)

Colorectal cancer

368

9 (2.4%)

Other cancer conditions

130

2 (1.5%)

Total Balearic Islands HC

1599

35 (2.2%)

Non-HC

3352

20 (0.6%)

Catalonian HC (Vargas-Parra 2022)

1848

14 (0.8%)

*Variants analysed (NM_007194): c.1427C > T, c.279G > A, c.349A > G, c.433C > T, c.1100del, c.591del, c.319+2T > A.

CHEK2 variants

% BOP cancer

% Colorectal cancer

% Other cancer conditions

% Non-HC

c.1427C > T

0.82

2.17

0.00

0.39

c.279G > A

0.73

0.27

0.77

0.21

Conclusion: The prevalence of P/LP variants in the HC cohort was found to be 2.2% (2.2% in BOP cancer patients and 2.4% in colorectal cancer patients), significantly higher than the genetically closest population of Catalonia. This possibly suggests the presence of a founder effect of c.1427C > T and c.279G > A variants, enriched in Mallorca and Ibiza patients, respectively.

Grants:

Conflict of Interest: None declared

P01.020.D Deciphering the Gene Expression Signature of High-Grade B-cell Lymphomas with 11q Aberrations

Emil Chteinberg 1, Gioia Di Stefano2, Henry Löffler-Wirth3, Annette M. Staiger4;5, Sina Hillebrecht1, Rabea Wagener1, Susanne Bens1, Kathrin Oehl-Huber1, Sonja Dahlum1, Dmitriy Abramov6, Birgit Burkhardt7, Abner Louissaint,Jr.8, Katrin Kurz5, Heike Horn4, Anja Mottok1;9, Raffaella Santi2, Ilske Oschlies10, Wolfram Klapper10, Kristian Schafernak11, Yanming Zhang12, Andreas Rosenwald9, Hans Binder3, Megan Limm12, German Ott5, Lorenzo Leoncini13, Sebastien Hergalant14, Coral DelVal1;15;16, Reiner Siebert1 1Ulm University and Ulm University Medical Center, Institute of human genetics, Ulm, Germany; 2University of Florence, Careggi University Hospital and Department of Health Sciences, 2 Pathology Section, Florence, Italy; 3Leipzig University, Interdisciplinary Centre for Bioinformatics (IZBI), Leipzig, Germany; 4University of Tübingen, Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany; 5Robert-Bosch-Hospital, Department of Clinical Pathology, Stuttgart, Germany; 6Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Department of Pathology, Moscow, Russian Federation; 7Münster University Hospital, Pediatric Hematology and Oncology, Münster, Germany; 8Massachusetts General Hospital, Department of Pathology, Boston, United States; 9Julius-Maximilians-University Würzburg, Department of Pathology, Würzburg, Germany; 10University of Kiel, Department of Pathology, Kiel, Germany; 11Phoenix Children’s Hospital, Department of Pathology and Laboratory Medicine, Phoenix, United States; 12Memorial Sloan Kettering Cancer Center, Department of Pathology and Laboratory Medicine, New York, United States; 13University of Siena, Department of Medical Biotechnologies, Section of Pathology, Siena, Italy; 14University De Lorraine, Inserm UMR 1256 Nutrition-Génétique et Exposition aux Risques Environnementaux (NGERE), Nancy, France; 15University of Granada, Andalusian Research Institute in Data Science and Computational Intelligence, Department of Computer Science and Artificial Intelligence, Granada, Spain; 16Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain

Consortium: ICGC-MMML-Seq Consortium

Background/Objectives: The 5th edition of the WHO Classification of Haematolymphoid Tumours describe disease entities defined by genetic abnormalities. For instance, the diagnosis of Burkitt lymphoma (BL) requires an IG::MYC juxtaposition, e.g. due to t(8;14)(q24;q32). Some high-grade B-cell lymphomas (HGBL) lacking the MYC translocation exhibit immunophenotypic similarities to BL but share similarities at the mutational level with diffuse large B-cell lymphomas (DLBCL). A subset of these HGBL (HGBL-11q) show characteristic chromosomal aberration defined by gains in 11q23.2-11q23.3 and losses in the 11q24.1-qter region. Here, we identify differential transcriptomic features of such HGBL-11q relative to BL and DLBCL.

Methods: Gene expression profiling was conducted using the HTG EdgeSeq Pan B-Cell Lymphoma Panel using RNA obtained from formal-fixed paraffin-embedded (FFPE) tissues of 7 BL, 26 HGBL-11q, 132 DLBCL, and two reactive tonsils. The panel was verified against RNAseq data available from overlapping samples of the ICGC-MMML-Seq cohort, leaving 206 genes for subsequent clustering and DESeq2 analyses. A two-step cumulative gene expression classifier was developed to segregate HGBL-11q from BL and DLBCL.

Results: Using unsupervised UMAP analysis of the 206 genes, we observed that HGBL-11q clustered apart from BLs and DLBCLs. DESeq2 revealed 48 and 38 genes differentially expressed between HGBL-11q and DLBCL or BL, respectively. A two-step classifier was trained to distinguish HGBL-11q from DLBCLs and BLs, respectively. PostHoc genomic analyses of cases classified as HGBL-11q showed two cases not yet assigned to this entity to carry typical 11q aberrations.

Conclusion: Gene expression profiling of FFPE tissues was effective in identifying HGBL-11q among other mature aggressive lymphomas.

Grants: None

Conflict of Interest: None declared

P01.021.A Germline ESR1 variants may be causative of juvenile papillomatosis of the breast

Zahra Firoozfar 1, Shahryar Alavi1, Mohammadreza Dehghani2, Mohammad Yahya Vahidi Mehrjardi3 1Palindrome, Isfahan, Iran; 2Yazd Reproductive Sciences Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran; 3Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran

Objectives: Germline variants are causative of 10% of cancer incidences. Juvenile papillomatosis of the breast (JPB), also known as Swiss cheese disease, is a benign condition occurs in individuals with a family history of breast carcinoma and its incidence in males is rare. Here, we report a case with several affected males by JPB or gynecomastia, harbouring a significant germline mutation in the ESR1 gene.

Methods: WES was performed on 200 Iranian individuals with hereditary cancers. Sequence raw data was analysed using GATK, and GRCh38 as reference genome. We also called copy number variations using PalinDepth, our proprietary algorithm. Variants were filtered based on the ACMG guideline, then were manually curated to find the best match with the patients’ phenotype.

Results: Germline ESR1 D538G mutation (chr6:g.152098791A > G) was detected in heterozygous state in a 5 years old boy suffering from JPB, with several males in the pedigree are affected with gynecomastia. No other significant exome variant was detected. Sanger sequencing showed that another affected family member is heterozygous for the ESR1 variant.

Conclusion: ESR1 D538G mutant is well described in sporadic breast cancer where ESR1 somatic mutations lead to malignancies. Recently it has been shown that ESR1 variants could increase the risk of hereditary breast cancer. Interestingly, we detected D538G mutation in a patient with familial breast anomalies in males. Further experiments could validate plausible effects of germline D538G mutation, investigating if this could trigger hereditary breast cancer in females.

Grants:

Conflict of Interest: None declared

P01.022.B Cascade testing for hereditary breast cancer: what is achievable in a South African clinical service?

Tabitha Osler1, Mardelle Schoeman2, Jennifer Edge3, Willem Pretorius2, Felix Rabe4, Christopher Mathew5, Michael Urban 6;7 1Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; 2Division of Molecular Biology and Human Genetics, University of Stellenbosch, Cape Town, South Africa; 3Department of Surgery, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; 4Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa; 5Sydney Brenner Institute for Molecular Bioscience, University of the Witwatersrand, Johannesburg, South Africa; 6Division of Human Genetics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; 7Department of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa

Background/Objectives: A main reason for genetic counselling and testing people with possible hereditary breast cancer is to identify probands and their asymptomatic family members who carry pathogenic variants, by the process of cascade testing. This allows prevention by radiographic screening and risk-reducing surgery, especially in female relatives. We investigated uptake in a South African regional breast cancer service.

Methods: Pedigrees and laboratory electronic records in 83 consecutive female breast cancer patients with pathogenic variants associated with high or moderate penetrance of hereditary breast cancer were used to assess family member testing. Electronic appointment, clinical and radiology records were used in test-positive relatives to identify preventive interventions conducted by a year later.

Results: 1173 family mem