Therefore, treatment with oral poly-adenosine diphosphate-ribose polymerase (PARP) inhibitors such as olaparib, which is an effective drug for patients with platinum-sensitive HBOC or HRD-positive ovarian cancer, can be used in patients with GC harboring BRCA1/2 mutations with PVs and/or HRD. Here, BRCA1 is linked to ovarian cancer.