Should tumor markers, such as carcinoembryonic antigen (CEA), be checked in a patient with a family history of colon cancer and severe narrowing at the rectosigmoid junction?

Tumor Marker Testing in Patients with Suspected Colorectal Cancer

Carcinoembryonic antigen (CEA) should not be used as a screening test for colorectal cancer, but it may be ordered preoperatively in patients with suspected colorectal cancer if it would assist in staging and surgical treatment planning. 1

Role of CEA in Diagnosis and Screening

• CEA has high specificity but very low sensitivity for identifying colorectal cancers, making it unsuitable for population screening 1, 2
• The American Society of Clinical Oncology (ASCO) explicitly recommends against using CEA as a screening test for colorectal cancer 1
• Endoscopy (colonoscopy or sigmoidoscopy) remains the main diagnostic tool for colorectal cancer, not tumor markers 1

Appropriate Use of CEA in Suspected Colorectal Cancer

Preoperative Assessment

• Preoperative CEA measurement is recommended to:
  • Assist in staging and surgical treatment planning 1
  • Establish a baseline for postoperative surveillance 1
  • Provide prognostic information 1, 2
• An elevated preoperative CEA (≥5 ng/mL) correlates with poorer prognosis regardless of tumor location 1, 2

For Patients with Rectosigmoid Narrowing

• For patients with severe narrowing at the rectosigmoid junction, endoscopy remains the primary diagnostic tool 1
• If family history of colorectal cancer is present, this increases risk and warrants thorough evaluation, but CEA is still not recommended as a screening test 1
• CT colonography might be valuable to precisely locate the tumor when endoscopy cannot explore the whole colon due to obstructive lesions 1

Limitations of CEA Testing

• Non-cancer related conditions can cause elevated CEA levels, including:
  • Inflammatory conditions (gastritis, diverticulitis)
  • Liver diseases
  • COPD
  • Diabetes
  • Smoking 2, 3
• CEA levels may be normal even in the presence of colorectal cancer, especially in early-stage disease 4, 5
• The sensitivity of CEA for early-stage disease (Dukes' A and B) is only about 36%, compared with 74% for Dukes' C and 83% for Dukes' D 1

Appropriate Tumor Marker Strategy

• For patients with suspected colorectal cancer:
  1. Perform complete colonoscopy or sigmoidoscopy with biopsy for histopathological confirmation 1
  2. If cancer is confirmed, then measure preoperative CEA 1
  3. Other recommended preoperative assessments include:
     • Complete blood count
     • Liver and renal function tests
     • Chest X-ray
     • CT scan of abdomen 1
• CA 19-9 is not recommended for screening, diagnosis, staging, surveillance, or monitoring treatment of patients with colorectal cancer 1

When CEA Testing is Valuable

• CEA is most valuable for:
  • Postoperative surveillance (every 3 months for stage II/III disease for at least 3 years) 1
  • Monitoring response to therapy in metastatic disease 1
  • Detecting recurrence, particularly liver metastases (sensitivity of 100% for liver metastases) 4

Common Pitfalls to Avoid

• Relying on CEA alone for diagnosis or screening of colorectal cancer 1, 3
• Failing to recognize that normal CEA levels do not exclude the presence of cancer 4, 5
• Not considering that elevated CEA levels can be caused by non-malignant conditions 2, 3
• Overlooking the need for histopathological confirmation through endoscopy and biopsy 1