Predictive value of carcinoembryonic antigen and carbohydrate antigen 19-9 related to downstaging to stage 0-I after neoadjuvant chemoradiotherapy in locally advanced rectal cancer.

Objective: To explore the value of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) in predicting downstaging to stage 0-I cancer after neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer.

Materials and methods: We respectively investigated pretreatment CEA, pretreatment CA19-9, posttreatment CEA, posttreatment CA19-9, pre-post-CA19-9 ratio, and pre-post-CEA ratio in 674 patients with locally advanced rectal cancer receiving nCRT and determined the patients' thresholds by using the receiver operating characteristic curve analysis. The association between downstaging (stage 0-I after nCRT), pathological complete response, and clinicopathological parameters was evaluated using the Pearson χ2 test. The clinicopathological parameters which were found to be significantly associated with downstaging were analyzed by logistic regression models and were incorporated into a scoring system.

Results: Multivariate analysis showed that pretreatment CA19-9 level, posttreatment CEA level, pre-post-CEA ratio, and pre-post-CA19-9 ratio were significantly correlated with downstaging. Area under the curve of the scoring system was higher than that of parameters alone.

Conclusion: The 4-factor scoring system with CA19-9 level, posttreatment CEA level, pre- post-CEA ratio, and pre-post-CA19-9 ratio is of more value in predicting downstaging to stage 0-I patients with locally advanced rectal cancer after nCRT than using the parameters alone.