BRCA1 and cholangiocarcinoma: Mutations in the most studied DDR genes BRCA1/2 fluctuates from 1% to 7% in patients with CCA; thus, after their success in pancreatic cancer, a plethora of studies aimed at investigating the response of CCA patients to PARP inhibitors, both in monotherapy and in combination with chemo and immunotherapy, are ongoing [43,48].