405P - HRD biomarkers in blood samples from BRCA1/BRCA2-associated advanced breast cancer (BC) patients (pts)

Background

PARP inhibitors (PARPi) are approved drugs for BC pts with germline BRCA1/BRCA2 mutations, as they elicit synthetic lethality in tumour cells with homologous recombination deficiency (HRD). However, over 40% of pts display intrinsic PARPi resistance, thus it is relevant to establish the HRD status before treatment initiation. We previously developed a test to quantify functional HRD by scoring RAD51 nuclear foci in tumour samples, and it showed an association with platinum response. Here, we aimed to study HRD biomarkers in blood, by identifying mutations in circulating tumour DNA (ctDNA) and by detecting RAD51 foci in circulating tumour cells (CTCs).

Methods

This is a longitudinal study that analysed blood and tumour samples from 24 advanced BC pts harbouring pathogenic variants in BRCA1/BRCA2 who were treated with a PARPi (<=2^nd line). Targeted capture ctDNA sequencing was performed in matched pre/on/post-treatment plasma samples using a custom panel of genes implicated in PARPi resistance. To analyse the status of HRD in Ficoll-isolated ex-vivo cultured CTCs, we optimized the RAD51 immunofluorescence (IF) assay previously developed for FFPE tumour samples.

Results

8/24 pts (33%) had triple negative BC (TNBC) and 6/24 (25%) had received previous platinum-based therapy as part of the early-stage or advanced disease treatment. ctDNA sequencing was feasible for all samples and identified BRCA1/BRCA2 reversion mutations in 1/24 (4%) pts at baseline and in 8/24 (33%) pts post-PARPi. The RAD51-IF tumour assay identified 11/12 (92%) available pre-treatment samples as HRD and 10/10 (100%) post-treatment samples as HRP. We enumerated CTCs in 10/12 additional samples (83%, 4 CTCs/ml [1-30]) and the RAD51-IF assay was feasible in 6/12 (50%), with 2/4 (50%) pre-treatment and 2/2 (100%) post-treatment samples showing a homologous recombination proficiency (HRP) status.

Conclusions

We report a low prevalence of BRCA1/BRCA2 reversion mutations prior to PARPi treatment in pts with low platinum pre-exposure. Testing for HRD by RAD51-IF in CTCs is a feasible challenge due to limitations in CTC isolation. In summary, blood tests provide valuable information of HRD evolution and PARPi resistance mechanisms, which complement tissue-based tests.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

FERO Foundation-GHD, La Marató TV3 (654/C/2019), ERA PerMed (ERAPERMED2019-215) with support from AECC and ISCIII.

Disclosure

V. Serra: Financial Interests, Institutional, Invited Speaker: AstraZeneca; Financial Interests, Personal, Advisory Board: GSK; Financial Interests, Personal, Other, WO2019122411A1: Methods based on the detection of rad51 foci in tumor cells: TBD; Financial Interests, Institutional, Research Grant, Testing various novel targeted agents in patient-derived tumour models: AstraZeneca. M. Oliveira: Financial Interests, Personal, Advisory Board: AstraZeneca, Cureo Science, Daiichi Sankyo / AstraZeneca, Gilead, Lilly, MSD, Pfizer, Relay Therapeutics, Roche, Seagen, iOne, iTEOS; Financial Interests, Personal, Invited Speaker: AstraZeneca, Eisai, Gilead, Lilly, Medscape, Pfizer, Roche, Seagen, MSD, Novartis; Financial Interests, Personal, Other, Educational activity: Libbs; Financial Interests, Personal, Coordinating PI: AstraZeneca; Financial Interests, Institutional, Local PI: AstraZeneca, Ayala Pharmaceuticals, Boehringer-Ingelheim, GSK, Gilead, Pfizer, Roche, Seattle Genetics, Zenith Epigenetics, Immutep; Financial Interests, Personal, Steering Committee Member: AstraZeneca; Financial Interests, Steering Committee Member: Roche; Non-Financial Interests, Member of Board of Directors, President elected 2023-2027: SOLTI Breast Cancer Research; Other, Travel Grant: AstraZeneca, Eisai, Gilead, Pierre Fabre. J. Mateo: Financial Interests, Personal, Advisory Board: AstraZeneca, Amgen, Janssen, Roche, Amunix, Pfizer; Financial Interests, Personal, Invited Speaker: AstraZeneca, MSD, Guardant Health; Financial Interests, Institutional, Advisory Board, Scientific Advisory Board Member for the company: Nuage Therapeutics; Financial Interests, Institutional, Research Grant: AstraZeneca, Pfizer Oncology, Amgen; Non-Financial Interests, Institutional, Product Samples, Access to drugs in early development for preclinical testing: AstraZeneca. A. Prat: Financial Interests, Personal, Invited Speaker: Roche; Financial Interests, Personal, Invited Speaker, Lecture fees: Novartis, Daiichi Sankyo; Financial Interests, Personal, Advisory Board, Advisory role/consultancy: Novartis, Pfizer, Peptomyc; Financial Interests, Institutional, Invited Speaker, Clinical trials: Daiichi Sankyo; Financial Interests, Institutional, Other, Contracted research: Boehringer, Medica Scientia inno. Research; Financial Interests, Personal, Advisory Board: AstraZeneca, Reveal Genomics, 1TRIALSP, S.L.; Financial Interests, Personal, Member of Board of Directors, Leadership role: Reveal Genomics, SL.; Financial Interests, Personal, Stocks/Shares: Reveal Genomics; Financial Interests, Personal, Royalties: Reveal Genomics, International Oncology Bureau, S.L.,; Financial Interests, Institutional, Local PI: Roche, AstraZeneca; Financial Interests, Personal and Institutional, Steering Committee Member: Daiichi Sankyo; Financial Interests, Institutional, Coordinating PI: Novartis; Financial Interests, Institutional, Funding: Reveal Genomics; Non-Financial Interests, Institutional, Other, Leadership roles: Patronage committee: Actitud Frente al Cáncer Foundation; Non-Financial Interests, Personal, Other, Asociación Española de Investigación sobre el Cáncer: ASEICA; Non-Financial Interests, Personal, Other, Research Foundation that gives grants to researchers: FERO. C.J. Lord: Financial Interests, Institutional, Research Funding: AstraZeneca, Artios; Financial Interests, Personal, Financially compensated role: AstraZeneca. A.N.J. Tutt: Financial Interests, Personal, Advisory Board, Breast Cancer Moonshot SAB: MD Anderson; Financial Interests, Personal, Invited Speaker, BRCA1/2 Mutagenesis, PARP inhibitors in early breast cancer: SABCS 2021; Financial Interests, Personal, Advisory Board, Trodelvy: Gilead; Financial Interests, Institutional, Advisory Board, CRUK expert panel Chairman: CRUK; Financial Interests, Institutional, Invited Speaker, Paid into research account at the Institute of Cancer Research: AZ Symposium ESMO 2021; Financial Interests, Institutional, Advisory Board, Paid into research institute account: GE Healthcare; Financial Interests, Personal, Advisory Board: EM Partners; Financial Interests, Institutional, Invited Speaker, Speaker at round table: VJ Oncology; Financial Interests, Institutional, Advisory Board: Gilead, AstraZeneca; Financial Interests, Institutional, Invited Speaker: Innovation in Breast Cancer Symposium 2022, AstraZeneca launch event; Financial Interests, Personal, Invited Speaker, Invited speaker at a Korean conference: GBCC; Financial Interests, Personal, Invited Speaker: Cancer Panel; Financial Interests, Personal, Other, Completion of survey: Research to Practise; Financial Interests, Personal, Other, AACR Team Science Prize: AACR Team Fund; Financial Interests, Personal, Invited Speaker, Speaker honorarium: Penn Medicine; Financial Interests, Institutional, Other, Partaking in meeting and slide mark up: Aicme; Financial Interests, Personal, Invited Speaker, Speaker for an event at GSTT hospital: AstraZeneca; Financial Interests, Institutional, Invited Speaker, Speaker at conference: SABCS 2022; Financial Interests, Institutional, Advisory Board, Part of SAB throughout 2023: PAGE Therapetics; Financial Interests, Institutional, Invited Speaker, Speaker at event: AstraZeneca; Financial Interests, Institutional, Invited Speaker, Invited speaker for Educational event: Gilead; Financial Interests, Institutional, Invited Speaker, Speaker honorarium: VHIO; Financial Interests, Institutional, Invited Speaker, This went to my KCL Institution: Livingston Memorial Symposium; Financial Interests, Personal, Full or part-time Employment, Head of Division for Breast Research, Director Breast Cancer Now Research Centre, Honorary Consultant Clinical Oncologist, Royal Marsden Hospital, joint leadership appointment with KCL that is processed through ICR payroll: Institute of Cancer Research; Financial Interests, Personal, Full or part-time Employment, Director of Breast Cancer Now Research Unit, King's College London, Honorary Consultant Clinical Oncologist, Breast Unit, Guy’s and St Thomas’ NHS Foundation Trust, joint leadership appointment with ICR that is processed through ICR payroll: King's College London; Financial Interests, Personal, Stocks/Shares: Inbiomotion; Financial Interests, Personal, Royalties, ICR rewards to inventor's payments paid to Andrew Tutt's research accounts at The Institute of Cancer Research and to personal accounts. These are associated with royalties paid to The Institute of Cancer Research (ICR) for the use of PARP inhibitors in DNA deficient cancers, licensee - AstraZeneca.: AstraZeneca; Financial Interests, Institutional, Coordinating PI, Financial support to my academic and hospital institutions for costs associated with global academic study chair and local site costs for OlympiA trial / travel expenses related to any trial related travel. Payments through Breast International Group for trial conduct in Olympic trial and through CRO's for commercial PARP inhibitor trial: AstraZeneca; Financial Interests, Institutional, Research Grant, Local site for a trial associated with DNA repair deficient TNBC: MERCK KGAA; Financial Interests, Institutional, Research Grant, Support for analysis of LAR subtype outcome in TNT trial: Medivation; Non-Financial Interests, Other, Member of Strategy Group: NCRI Strategy Group; Non-Financial Interests, Other, Member of the Committee: ESMO Guidelines Committee; Non-Financial Interests, Officer, Committee Member: ESMO 2023 Scientific Committee; Non-Financial Interests, Other, Consensus panel member: St Gallen; Non-Financial Interests, Institutional, Product Samples, Responsible for care of patients receiving Olaparib on named patient programme in Breast Cancer @ Guy's London: Guy's Hospital; Other, BCN as a charity receive payments through AstraZeneca related to PARP inhibitor patents. independent of this I receive BCN grants to study homologous recombination deficient breast and other cancers,: Breast Cancer Now; Other, CRUK as a charity receive payments through AstraZeneca related to PARP inhibitor patents. independent of this I receive BCN grants to study homologous recombination deficient breast and other cancers,: CRUK. A. Llop-Guevara: Financial Interests, Personal, Full or part-time Employment: AstraZeneca. J. Balmaña: Financial Interests, Personal, Invited Speaker: AstraZeneca; Financial Interests, Institutional, Other, Educational programs: AstraZeneca -MSD; Financial Interests, Institutional, Steering Committee Member: AstraZeneca; Financial Interests, Institutional, Local PI: MedSir. All other authors have declared no conflicts of interest.