KRAS and colorectal carcinoma: Coexisting PIK3CA and KRAS mutations, which occur in approximately 8%–9% of CRC cases [55,66,67,68,73,74,75,76,77,78], predict resistance to anti-EGFR therapy, as well as worse prognosis, in CRC [16,39,52,55,66,68,76,79,80,81,82,83,84,85,86].