BRCA1 and cancer: Likewise, although the concept of BRCAness (cancers that phenocopy cancers with BRCA1/2 mutations [68,75,76]) has proven useful in extending the use of PARPi beyond those individuals with BRCA1 or BRCA2 mutant cancers to those with a homologous recombination defect caused by some other means (e.g. mutation in PALB2, RAD51C, RAD51D), there is the implicit assumption that each of these other defects causes a similar extent of PARPi sensitivity as for a deleterious BRCA1 or BRCA2 mutation.