Patients with tumours that harbour BRCA mutations are more likely to respond to PARP inhibition, and identifying these patients is now well established in clinical practice. A BRCA mutation detected in a tumour can be germline or somatic in origin. A blood test to detect BRCA mutations in DNA isolated from whole blood samples is required to determine if the mutation is germline (blood test positive) or somatic (blood test negative). Somatic (sBRCA) mutation status is determined by tumour (tBRCA) sequencing and germline (gBRCA) mutation testing in blood.
Most indications require patient identification prior to treatment using BRCA testing for germline or somatic mutations. Accordingly, companion diagnostics have been developed to aid this process, and an up-to-date list of FDA approved companion diagnostics can be found at www.fda.gov.
Outside of the US, BRCA testing does not have to be done by specific companies, but can be performed by any certified laboratory.
Other biomarker tests are also being investigated to identify patients with genetic alterations beyond BRCA1/2 that are more likely to respond to PARP inhibitors and agents targeting DDR [1-10].
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