In patients with HGSOC enrolled in the ARIEL2 Part 1 PARPi study [122], zygosity of BRCA1 methylation was extensively analyzed in archival tumor and pre-treated biopsy samples with a quantitative method [123], and patients with homozygous BRCA1 methylation showed improved clinical outcomes with rucaparib treatment, compared to those with any methylated BRCA1 ever, indicating that homologous BRCA1 methylation is more likely to respond to PARPi, and that heterologous methylation is likely to be associated with resistance. This evidence concerns the gene BRCA1 and neoplasm.