What does a CEA (Carcinoembryonic Antigen) test measure?

What CEA Tests For

CEA (Carcinoembryonic Antigen) is a glycoprotein tumor marker measured in blood that is primarily used for monitoring colorectal cancer recurrence and treatment response, not for cancer screening or diagnosis. 1

Basic Characteristics of CEA

• CEA is a glycoprotein with beta-globulin electrophoretic mobility, sedimentation coefficient of 7-8S, and molecular weight of approximately 200,000 daltons that can be detected and measured by radioimmunoassay 2

• Normal CEA levels are typically defined as less than 2.5-5 ng/mL, though 5 ng/mL may be a more realistic threshold for clinical significance 2, 1

• CEA is not cancer-specific and is normally expressed in various tissues throughout the body 3

What Conditions Elevate CEA

Malignant Conditions

• Colorectal cancer is the primary malignancy associated with CEA elevation, with 50-60% of patients with metastatic disease showing elevated levels 4

• Other gastrointestinal cancers including pancreatic and gastric malignancies demonstrate CEA elevation in just over 50% of cases 5

• Breast cancer shows CEA elevations in 40-73% of patients across stages I-IV, and 80% of patients will have CEA elevation 3-10 months prior to clinical symptoms of recurrence 5

• Lung cancer, particularly bronchogenic carcinoma, shows elevated preoperative CEA in 77% of patients, though smoking confounds interpretation 5

• Cholangiocarcinoma demonstrates CEA elevation in approximately 30% of patients 6

• Other epithelial malignancies including cervical, uterine, and ovarian cancers produce CEA in 47-75% of cases 5

Benign Conditions That Elevate CEA

• Inflammatory bowel disease (gastritis, peptic ulcer disease, Crohn's disease, ulcerative colitis) can elevate CEA levels 6, 2

• Liver diseases including cirrhosis and hepatitis cause CEA elevation 6

• Benign extrahepatic biliary obstruction elevates CEA, with highest levels occurring when coexistent cholangitis or liver abscess is present 6

• Pulmonary conditions including chronic obstructive pulmonary disease and lung fibrosis are associated with elevated CEA 3

• Smoking history influences serum CEA levels and can cause elevations up to 10 ng/mL in otherwise healthy individuals 2

• Advanced age (>65 years) is independently associated with higher baseline CEA levels 3

• Uremia and chronic kidney disease can elevate CEA 3

Clinical Applications of CEA Testing

What CEA Should NOT Be Used For

• CEA is NOT recommended as a screening test for colorectal cancer due to low sensitivity and specificity, particularly for early-stage disease 1, 4

• CEA should NOT be used for cancer diagnosis as only 20-90% of colorectal carcinomas show elevation depending on tumor spread, and many non-malignant conditions cause false positives 7, 8

• CEA alone cannot confirm or rule out suspected cancer with sufficient diagnostic certainty 8

Appropriate Uses of CEA

Preoperative Staging (Colorectal Cancer):

• CEA may be ordered preoperatively if it would assist in staging and surgical treatment planning 1
• Elevated preoperative CEA (≥5 ng/mL) correlates with poorer prognosis regardless of tumor stage, though data are insufficient to use this for determining adjuvant therapy 1, 6

Postoperative Surveillance (Colorectal Cancer):

• Postoperative CEA should be performed every 3 months for stage II or III disease for at least 3 years if the patient is a candidate for surgery or chemotherapy of metastatic disease 1
• An elevated CEA, if confirmed by retesting, warrants further evaluation for metastatic disease with CT imaging of chest, abdomen, and pelvis 6
• CEA was the most cost-effective approach to detecting potentially resectable metastases, with 64% of recurrences detected first by CEA in surveillance studies 1
• Surveillance should be delayed until after completion of adjuvant chemotherapy, as chemotherapy may falsely elevate CEA levels 1

Monitoring Treatment Response (Metastatic Disease):

• CEA is the marker of choice for monitoring metastatic colorectal cancer during systemic therapy 1, 4
• CEA should be measured at the start of treatment and every 1-3 months during active treatment 1, 4
• Persistently rising CEA values above baseline suggest progressive disease even in the absence of corroborating radiographs 1, 4
• Caution is needed when interpreting rising CEA during the first 4-6 weeks of new therapy, as spurious early rises may occur, especially after oxaliplatin 1, 4, 9

Breast Cancer Monitoring:

• CEA can be used for monitoring metastatic breast cancer during active therapy in conjunction with diagnostic imaging, history, and physical examination 6, 4
• CEA is NOT recommended for screening, diagnosis, staging, or routine surveillance after primary breast cancer therapy 4

Critical Interpretation Caveats

• An elevated CEA alone does NOT justify initiation of systemic therapy for presumed metastatic disease without radiographic or pathologic confirmation 6

• Two CEA values above baseline are adequate to document progressive disease even without corroborating radiographs in the metastatic setting 1

• CEA has high specificity but low sensitivity, making it unsuitable for population screening but useful for monitoring known disease 6

• The CEA half-life after tumor resection is several days, allowing detection for weeks post-resection, which provides practical advantages for monitoring compared to other biomarkers 9