FBXW7 is a tumor suppressor gene responsible for the degradation of several proto-oncogenes. mTOR is one of the substrates of FBXW7-mediated protein degradation, and loss of function of FBXW7 increases the levels of total and activated mTOR. Codons 465 and 505 are some of the most frequently mutated sites in the FBXW7 gene. FBXW7 is mutated in approximately 15% of small bowel cancers. Preclinical data have suggested that inactivating mutations of FBXW7 could predict sensitivity to the mTOR inhibitor rapamycin; however, the clinical utility remains unknown.