Tumor Marker Index Based on CEA and CA19-9 as a Prognostic Biomarker in Resectable Colon Cancer

Despite curative resection, the prognosis after surgery for colon cancer varies considerably even among patients within the same TNM stage. There is a need for reliable biomarkers to complement the TNM classification. In pancreatic cancer, tumor markers have been reported as indicators of biological resectability. We therefore focused on tumor markers in colon cancer and investigated the prognostic significance of the tumor marker index (TMI).

We retrospectively reviewed patients with colon cancer (cecum to rectosigmoid) who underwent curative resection at our institution between 2011 and 2023. Among them, 361 patients without missing clinical or laboratory data were included. TMI was defined as the product of preoperative serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) levels. Patients were stratified into low- and high-TMI groups based on cutoff values determined by receiver operating characteristic (ROC) curve analysis with recurrence as the outcome. Three-year recurrence-free survival (3y-RFS), local recurrence-free survival (3y-LRFS), and distant metastasis-free survival (3y-DMFS) were compared between groups.

The optimal TMI cutoff value was 64, with 226 cases classified into the low-TMI group and 135 cases into the high-TMI group. The 3y-RFS rate was significantly higher in the low-TMI group than in the high-TMI group (94.0% vs. 88.4%, p=0.023). Similarly, the 3y-LRFS rate was significantly better in the low-TMI group (97.7% vs. 95.2%, p=0.044). In contrast, there was no significant difference in 3y-DMFS between the low- and high-TMI groups (95.4% vs. 91.4%, p=0.103).

TMI was associated with postoperative recurrence patterns in curatively resected colon cancer. TMI may serve as a simple and clinically useful biomarker to complement TNM staging and improve risk stratification after curative surgery.