In a 2021 case study, a 64-year-old female patient with recurrent MSI-stable CRC with KRAS wild-type mutations, who had refractory CRC to oxaliplatin- and irinotecan-based chemotherapy combined with bevacizumab, demonstrated prolonged SD with third-line regorafenib and the PD-1 inhibitor sintilimab combination treatment [21]. The gene discussed is KRAS; the disease is colorectal carcinoma.