In survival analysis, we found that PIK3CA exon 20 was an adverse biomarker in stage IV CRC patients, and Stage III patients with PIK3CA mutation were more likely to have disease recurrence than those with wild-type PIK3CA. We also found that PIK3CA exon 9 mutations is not a negative biomarker for wild-type KRAS, NRAS, and BRAF mCRC patients in cetuximab treatment. The gene discussed is KRAS; the disease is colorectal carcinoma.