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Functional RECAP (REpair CAPacity) assay identifies homologous recombination deficiency undetected by DNA-based BRCAness tests.

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Nguyen, Luan 
Van Hoeck, Arne 
Sieuwerts, Anieta M 
Verkaik, Nicole S 


Germline BRCA1/2 mutation status is predictive for response to Poly-[ADP-Ribose]-Polymerase (PARP) inhibitors in breast cancer (BC) patients. However, non-germline BRCA1/2 mutated and homologous recombination repair deficient (HRD) tumors are likely also PARP-inhibitor sensitive. Clinical validity and utility of various HRD biomarkers are under investigation. The REpair CAPacity (RECAP) test is a functional method to select HRD tumors based on their inability to form RAD51 foci. We investigated whether this functional test defines a similar group of HRD tumors as DNA-based tests. An HRD enriched cohort (n = 71; 52 primary and 19 metastatic BCs) selected based on the RECAP test (26 RECAP-HRD; 37%), was subjected to DNA-based HRD tests (i.e., Classifier of HOmologous Recombination Deficiency (CHORD) and BRCA1/2-like classifier). Whole genome sequencing (WGS) was carried out for 38 primary and 19 metastatic BCs. The RECAP test identified all bi-allelic BRCA deficient samples (n = 15) in this cohort. RECAP status partially correlated with DNA-based HRD test outcomes (70% concordance for both RECAP-CHORD and RECAP-BRCA1/2-like classifier). RECAP selected additional samples unable to form RAD51 foci, suggesting that this functional assay identified deficiencies in other DNA repair genes, which could also result in PARP-inhibitor sensitivity. Direct comparison of these HRD tests in clinical trials will be required to evaluate the optimal predictive test for clinical decision making.



Antineoplastic Agents, BRCA1 Protein, BRCA2 Protein, Breast Neoplasms, DNA, Female, Homologous Recombination, Humans, Poly(ADP-ribose) Polymerase Inhibitors, Poly(ADP-ribose) Polymerases, Recombinational DNA Repair

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Springer Science and Business Media LLC
KWF Kankerbestrijding (EMCR 2008-4045, EMCR 2014-7048)
KWF Kankerbestrijding (Dutch Cancer Society) (EMCR 2014-7048, EMCR 2008-4045)