The use of PARP inhibitors (PARPi) to treat BRCA1/2-mutant or homologous recombination (HR)-deficient tumors has been studied in various cancers, and is referred to as ‘synthetic lethality’ (Bryant et al., 2005; Farmer et al., 2005; Parvin et al., 2019). This evidence concerns the gene PARP1 and cancer.