Correlation between circulating tumor DNA and carcinoembryonic antigen levels in patients with metastatic colorectal cancer

Background Circulating tumor DNA (ctDNA) is a biomarker with potential to reflect comprehensive genomic information and overcome intratumor heterogeneity. In contrast, carcinoembryonic antigen (CEA) is a conventional tumor marker for predicting recurrence, survival, and chemotherapeutic efficacy in patients with metastatic colorectal cancer (mCRC). However, the relationship between them remains unclear. Here, the relationship between plasma ctDNA and CEA levels was evaluated to clarify the advantages and disadvantages of their clinical use. Methods A total of 110 patients with mCRC underwent chemotherapy were enrolled. Amplicon-based plasma genomic profiling of 14 genes that are commonly mutated in CRC by next-generation sequencing was compared to the CEA level and tumor diameter using Spearman's correlation coefficient. Results The overall concordance rate between the ctDNA and CEA levels was 75.5% (83/110). The correlation coefficient between the ctDNA and CEA levels was lower in the group of patients without liver and lymph node metastases (r = 0.18, p = 0.44) than in the group of patients with liver metastasis (r = 0.48, p < 0.0001). Although the correlation coefficients between tumor diameter and both ctDNA and CEA levels were high in the group of patients with liver metastasis, only the CEA correlation coefficient was maintained in the group of patients without liver and lymph node metastases (r = 0.53, p = 0.01). The characteristics that influenced discordance were liver metastasis and the sum of tumor diameter. Conclusions The status of ctDNA and CEA may not be consistent in patients with mCRC without liver metastasis or with a low tumor volume; both results should be considered when deciding a treatment strategy.

Automated summary

This study evaluated the relationship between plasma ctDNA and CEA levels in patients with mCRC, finding a lower correlation coefficient in patients without liver and lymph node metastases. The correlation coefficients between tumor diameter, ctDNA, and CEA levels varied depending on the presence of liver metastasis, highlighting the importance of considering both ctDNA and CEA results in treatment decision-making for mCRC patients.