This study aims to provide information about the genomics of your breast cancer which your oncologist can use to enhance the treatment of your disease possibly enabling more targeted and personalised therapy.This study will carry out TruSight Oncology Comprehensive (TSOComprehensive) testing on breast cancer tumour tissue that was collected at the time of your breast cancer diagnosis or during your breast surgery or if you have brain metastasis and you have had a biopsy for this. The TruSight Oncology Comprehensive assay is a next-generation sequencing (NGS) test used to analyse cancer-related genomic changes in patients, offering a comprehensive view of potential mutations and other alterations that can impact treatment decisions. The TruSight Oncology Comprehensive assay is CE-IVD marked for use in Europe, meaning that it complies with the relevant EU regulation, for comprehensive genomic profiling for different types of cancer. It analyses 523 cancer-relevant genes from both DNA and RNA to identify variations. It will also look for changes and mutations which may affect cell growth and stability. By identifying relevant mutations and biomarkers, the assay can help oncologists select the most appropriate treatment strategies with the aim of improving patient outcomes.

This is a pragmatic single-arm diagnostic interventional study. The study will use the Illumine TruSight Oncology 500 assay for research use only under Article 5(5) in-house exemption of the EU IVDR (EU 2017/746). Testing will be performed on paraffin embedded tumour tissue. This assay will target 523 genes to assess all somatic DNA variants as well as microsatellite instability (MSI), tumour mutational burden (TMB), and homologous recombination deficiency (HRD). Testing will be performed centrally in the molecular diagnostics laboratory (ISO 15189 accredited) at Beaumont hospital on the Next Seq 550Dx. This lab currently uses this platform for diagnostic comprehensive genomic profiling. Bioinformatic analysis will be undertaken to identify clinically actionable mutations. Results will be discussed at the multi-disciplinary Molecular Tumour Board, Beaumont RCSI Cancer Centre and full data along with treatment recommendation will be provided to the treating oncology team.

Inclusion Criteria:

1. Patients diagnosed with primary breast cancer attending hospital for the resection of their tumour tissue. Or Patients with suspected or confirmed brain metastatic breast cancer (Patient has a history of a biopsy or surgically (i.e. pathologically) confirmed primary breast cancer) attending hospital for the resection/biopsy and/or treatment of their tumour tissue. Or Patients with suspected (but not necessarily biopsy confirmed) newly diagnosed brain metastatic breast cancer attending hospital for the resection/biopsy and/or treatment of their tumour tissue.
2. Patients receiving neoadjuvant treatment are also eligible (if applicable).
3. Patients must be ≥ 18 years of age.
4. Patients must be able to give informed consent.

Exclusion Criteria:

1. Patients who do not have a confirmed diagnosis of primary breast cancer.
2. Patients whose participation, in the opinion of the PI, would not be in their best interest, or those whom in the opinion of the PI would be unsuitable for study for reasons of infirmity or poor health.