Primary cancers of the appendix are rare and are frequently diagnosed after surgery for appendicitis. There is no designated staging system or evidence-based guideline for treatment. The staging and treatment of appendiceal adenocarcinoma mirror that of colon cancer. Elevated serum carcinoembryonic antigen (CEA) has been strongly associated with poor prognosis in colorectal cancer, so our study aims to first compare appendiceal cancers with tumors of the ascending colon, and then evaluate the prognostic value of CEA in appendiceal cancers.
We performed a retrospective analysis of all patients (n = 2,614) diagnosed with appendiceal adenocarcinoma from 2004 to 2014 in the National Cancer Institute’s Surveillance, Epidemiology and End Results database. All appendiceal cancer patients were designated as either elevated (C1) or normal (C0) based on the pretreatment serum CEA level. We performed univariate and multivariate analyses to compare appendiceal cancer characteristics to tumors of the ascending colon (n = 73,057), then identified independent factors associated with CEA elevation in appendiceal cancers.
Upon multivariate analysis, compared to tumors of the ascending colon, appendiceal cancers are significantly more likely (P < 0.05) to have higher stage at diagnosis (OR 2.95, 1.19, 6.56 for stage 2, 3, and 4). They are less likely to have the CEA test ordered (OR 0.31). Appendiceal cancers are being diagnosed more in recent years (OR 1.90, 2.11, 1.86 for years 2012, 2013, and 2014) while colon cancer incidence is remaining the same. Compared to C0 appendiceal cancers, C1 cancers are more likely to have higher tumor grade (OR 6.56 and 5.50 for grade 2 and 3) and higher overall stage (OR 1.96, 2.44, 9.60 for stage 2, 3, and 4).
Though appendiceal cancers are rare, they are increasing in incidence. They are less likely than colorectal cancers to have the CEA test ordered despite CEA elevation odds ratio having no significant difference between the two cancers. Elevated CEA in appendiceal cancers is associated with later stage and higher grade. CEA levels should be checked in all appendiceal cancer patients to assist in the development of treatment strategies.
Clinical trial identification
Has not received any funding.
All authors have declared no conflicts of interest.