RESUMEN
There are differences in the incidence, clinical presentation, molecular pathogenesis, and outcome of colorectal cancer (CRC) based on tumor location. Emerging research suggests that the perioperative carcinoembryonic antigen (CEA) ratio (post-op/pre-op CEA) is a prognostic factor for CRC patients. We aimed to determine the association between CEA ratio, tumor location, and overall survival (OS) among patients with CRC. We analyzed 427 patients who underwent resection for CRC at the University of Kansas Medical Center. After excluding those without pre- or post-operative CEA data, 207 patients were classified as either high (≥0.5) or low (<0.5) ratio. Primary outcomes were as follows: (1) OS stratified by CEA ratio; (2) OS stratified by tumor location; (3) OS stratified by tumor location among those with CEA elevation > 5 ng/mL at the time of recurrence. The Kaplan-Meier method was used to estimate survival rates. The median age was 62 years (inter-quartile range 51-71), 55% were male, 41% were smokers, 71% had left-sided tumors, the median pre-operative CEA was 3.1 ng/mL (inter-quartile range (IQR) 1.5-9.7), and 57% had a CEA ratio ≥0.5. The OS rates were 65.1% and 86.3% in patients with high versus low CEA ratios, respectively (log-rank p-value = 0.045). The OS rates were 64.4% and 77.3% in patients with right-sided vs. left-sided tumors, respectively (log-rank p-value = 0.5). Among patients with CEA levels greater than 5 at the time of recurrence, the OS rates were 42.9% and 43.4% in patients with right-sided vs. left-sided tumors, respectively (log-rank p-value = 0.7). There was a significantly higher survival among patients with low CEA ratios than among those with high CEA ratios. There was no difference in OS between left- versus right-sided tumors. Among patients with CEA elevation > 5 ng/mL at the time of recurrence, there was no difference in OS between left versus right-sided tumors. These findings warrant validation in a larger cohort as our sample size was limited.