Can we optimize the CEA as a response marker in rectal cancer

INTRODUCTION CEA is a biomarker commonly used in colorectal cancer, however its use as a prognostic value is still controversial. Recent studies demonstrate that CEA produced locally by tumor cells has a higher prognostic value compared to serum CEA. It is intended to determine whether there is an association between the CEA/tumor size ratio (CEA/ExT) and the pathological tumor response in patients with rectal adenocarcinoma (ADC), submitted to neoadjuvant chemoradiotherapy (N-CRT), followed by surgical tumor resection. METHODS Retrospective study of rectal ADC patients undergoing N-CRT followed by curative surgery between March/2012 and October/2017. Analysis of CEA and tumor extension for pre-treatment CEA/ExT calculation, as well as the pathological response in the surgical specimen after treatment. RESULTS 89 patients were included, 60.7% men, mean age 63.8 ± 10.42. There was a good response to N-CRT in 41.6% of the patients, tumor downstaging in 83.1% and a complete pathological response in 23.6%. The average CEA/ExT was 2.01ng/ml/cm. In the univariate analysis, higher CEA/ExT values ​​were related to a lower frequency of pathological response (p = 0.04) and to a lower frequency of tumor downstaging (p = 0.02). In the multivariate analysis, CEA/ExT was independently related to tumor downstaging (OR: 0.72; 95% IC-0.53-0.98, p-0.036). CONCLUSIONS lower pre-treatment CEA/ExT values ​​seem to be associated with tumor downstaging, and this parameter may be promising as a predictor of a more favorable response in patients with rectal ADC undergoing treatment with N-CRT.