XRCC1 and familial pancreatic carcinoma: However, the role of XRCC1 in tumors is contradictory; low expression levels of XRCC1 were observed in gastric and pancreatic cancer and were related to invasiveness [6, 7], but a high expression of XRCC1 was observed in head and neck squamous cell carcinoma and was related to a worse patient prognosis [8].