Previous studies have proposed homologous DNA repair deficiency (HRD) biomarkers, such as BRCA1/2 mutation,24, 25 BRCA1 promoter methylation,26–28 ‘BRCAness’ expression and CGH signatures,27, 29 Fanconi F and D methylation or loss,30 p53 and PTEN loss of function mutations or expression level,31–33 cell line based HRD/PARPi signatures,34 telomeric allelic imbalance,35 loss of heterozygocity HRD scoring,36 and HRD ‘genomic scarring’,37 among others,27, 38, 39 as possible markers of sensitivity to PARP inhibition. The gene discussed is BRCA1; the disease is DNA repair disease.