What are the tumor markers for colorectal cancer (Colonic Ca)?

From the Guidelines

Carcinoembryonic antigen (CEA) is the primary tumor marker used for colorectal cancer monitoring, and it should be ordered preoperatively to assist in staging and surgical planning, and postoperatively every 3 months for at least 3 years in patients with stage II or III disease. The use of CEA for screening is not recommended due to its limited sensitivity and specificity 1. CEA is most valuable for surveillance after treatment, and rising CEA levels may indicate recurrence, with further evaluation warranted if confirmed by retesting 1. Other markers, such as CA 19-9, may be elevated in colorectal cancer but lack specificity, and molecular markers like KRAS, BRAF, and microsatellite instability status are increasingly important for treatment decisions rather than diagnosis 1.

Key Points

• CEA should be used preoperatively to provide prognostic information and to assess its utility for postoperative surveillance 1
• Postoperative serum CEA testing should be performed every 3 months in patients with stage II or III disease for at least 3 years after diagnosis 1
• CEA is the marker of choice for monitoring metastatic colorectal cancer during systemic therapy, and it should be measured at the start of treatment and every 1-3 months during active treatment 1
• CA 19-9 is not recommended for screening, diagnosis, staging, surveillance, or monitoring treatment of patients with colorectal cancer, but it can be measured every 1-3 months during active treatment for locally advanced or metastatic disease 1

Important Considerations

• CEA levels should be interpreted cautiously as they can be elevated in non-malignant conditions, including smoking, inflammatory bowel disease, liver disease, and other gastrointestinal disorders 1
• The absolute CEA value is less important than the trend over time, with normal levels generally below 5 ng/mL in non-smokers and below 7.5 ng/mL in smokers 1

From the Research

Tumor Markers for Colonic Cancer

• Carcinoembryonic antigen (CEA) is the most established and clinically useful tumor marker for colorectal cancer 2, 3, 4, 5, 6
• CEA levels can serve as an indicator of successful or incomplete resection, and are useful in monitoring the effect of chemotherapy or radiotherapy 2
• Elevated CEA levels are associated with advanced or metastatic disease and poorer prognosis 3, 5
• CEA measurement has an important role in the investigation, management, and follow-up of patients with colorectal cancer 3
• Other tumor markers, such as carbohydrate antigen (CA 19-9), tissue polypeptide specific antigen (TPS), and tumor-associated glycoprotein-72 (TAG-72), have also been used to recognize colorectal cancer, but none have excellent diagnostic accuracy 6
• Recent studies have explored the use of hematopoietic growth factors and various enzymes in the diagnosis and prognosis of colorectal cancer 6
• Analysis of circulating cancer cells (CTCs) may be a source of information useful in the treatment of patients with colorectal cancer 6

Limitations of Tumor Markers

• CEA is neither sensitive nor specific enough to be used in routine screening for possible malignancy in an asymptomatic population 2
• CEA levels alone are not sufficient to improve survival rates 3
• Currently available markers have significant limitations, and most cancer deaths are not caused by the primary tumor itself but by its spread 6