Background. Appendiceal adenocarcinomas (AAs) are rare and this has limited their molecular understanding. The purpose of our study was to characterize the molecular profile of AA and explore the role of targeted therapy against cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR). Patients and Methods. Weperformedaretrospectivereviewof 607 patients with AA at a single institution. A total of 149 patients underwent molecular testing for at least one of the following: activating mutations in KRAS, BRAF, cKIT, EGFR, or PI3K; protein expression of c-KIT or COX-2; or microsatellite instability (MSI) status by immunohistochemistry. Kaplan-Meier product limit method and log-rank test were used to estimate overall survival (OS)andtodetermineassociationsamongOS,COX-2expression, KRAS mutations, and other characteristics. Results. Age, grade, stage, signet ring cells, mucinous histology, and completeness of cytoreduction score correlated with survival outcomes. COX-2 expression, KRAS, PI3K, and BRAF mutations were seen in 61%, 55%, 17%, and 4% of patients, respectively. High MSI was seen in 6% of patients. KRAS mutation was strongly associated with well differentiated or moderately differentiated AA (p Ͻ .01). COX-2 expression (p ϭ .33) and the presence of KRAS mutation (p ϭ .91) had no impact on OS. The use of celecoxib in patients whose tumors expressed COX-2 (p ϭ .84) and the use of cetuximab or panitumumab in patients with KRAS wild-type tumors (p ϭ .83) also had no impact on OS.
Conclusion.In this cohort, we demonstrated that COX-2 expression and KRAS mutations were frequently seen in AA, although neither exhibited any prognostic significance. MSI was infrequent in AA. Targeted therapy against COX-2 and EGFR appeared to provide no clinical benefit. Well and moderately differentiated AA were molecularly distinct from poorly differentiated AA. The Oncologist 2013;18:1270 -1277 Implications for Practice: Appendiceal adenocarcinomas (AAs) are rare, and current understanding of their molecular biology is poor. Surgical resection is the mainstay of therapy. Limited data exists to guide medical management, and the role of targeted therapy in AAs has not been studied. This study endeavors to define molecular alterations in AAs. Activating KRAS mutations represent the most common alteration, occurring in 55% cases. Interestingly, well and moderately differentiated tumors demonstrate similar high rates of KRAS mutation, contrary to the low rates seen in poorly differentiated tumors. These data link clinical behavior with molecular biology and suggest that moderately differentiated tumors resemble well-differentiated tumors and should be treated similarly. Further prospective trials are needed to evaluate the efficacy of targeted therapies such as antiepidermal growth factor receptor therapy in AAs, prior to their implementation in clinical practice. Constructing a molecular sketch of AAs is a necessary first step toward recognizing molecular pathways involved in their carcinogenesis and advancing the ro...