Carcinoembryonic Antigen (CEA) Test: Purpose and Interpretation
CEA should not be used for cancer screening or diagnosis, but serves as the marker of choice for monitoring colorectal cancer recurrence after curative resection and for assessing treatment response in metastatic disease. 1, 2
Primary Clinical Applications
Preoperative Use in Colorectal Cancer
- Order CEA preoperatively in patients with colorectal carcinoma to provide prognostic information and establish a baseline for postoperative surveillance. 1
- Elevated preoperative CEA (≥5 ng/mL) correlates with poorer prognosis, though this alone does not determine adjuvant therapy decisions. 1
- Preoperative CEA measurement is particularly valuable in patients being considered for resection of liver or pulmonary metastases, as it provides important prognostic information. 1
Postoperative Surveillance for Stage II-III Disease
- Measure CEA every 3 months for at least 3 years after curative resection in patients with stage II or III colorectal cancer who are candidates for surgery or systemic therapy. 1
- CEA is the most cost-effective test for detecting potentially resectable metastases, identifying 64% of recurrences before other modalities. 1
- An elevated CEA must be confirmed by retesting before proceeding with further evaluation. 1, 3
- An elevated CEA warrants comprehensive imaging (CT chest, abdomen, pelvis) to identify metastatic disease, but does not justify starting treatment without radiographic or pathologic confirmation. 1, 3
Monitoring Metastatic Disease During Treatment
- CEA is the marker of choice for monitoring metastatic colorectal cancer during systemic therapy. 1, 2
- Measure CEA at treatment initiation and every 1-3 months during active therapy. 1
- Persistently rising CEA values above baseline indicate progressive disease even without radiographic confirmation, and should prompt restaging. 1
Critical Interpretation Pitfalls
False Elevations and Timing Considerations
- Exercise caution when interpreting rising CEA during the first 4-6 weeks of new chemotherapy, as spurious early rises occur, particularly with oxaliplatin. 1, 3, 2
- Chemotherapy-induced changes in liver function can transiently elevate CEA independent of disease progression. 1
Non-Malignant Causes of Elevation
- Multiple benign conditions elevate CEA including: gastritis, peptic ulcer disease, diverticulitis, liver diseases (including biliary obstruction with cholangitis), chronic obstructive pulmonary disease, diabetes, inflammatory bowel disease, and any acute or chronic inflammatory state. 1, 3
- Always consider and exclude non-cancer causes before attributing CEA elevation to malignancy. 3
Limitations and Contraindications
Why CEA Fails as a Screening Test
- CEA has insufficient sensitivity (only 50-60% of patients with metastatic colorectal cancer have elevated levels) and specificity for cancer screening or diagnosis. 2, 4
- Even at a low threshold of 2.5 µg/L, sensitivity is only 82% with specificity of 80%, generating excessive false alarms. 4
- CEA must be augmented with other diagnostic modalities; it cannot be used alone for cancer detection. 4
Breast Cancer Applications
- CEA is not recommended for screening, diagnosis, staging, or routine surveillance in breast cancer. 1, 2
- In metastatic breast cancer, CEA can be used alongside imaging and clinical assessment for monitoring treatment response, but only when readily measurable disease is absent. 1
Optimal CEA Threshold Selection
When using CEA for surveillance, apply a threshold of 10 µg/L rather than lower values to maximize specificity (97%) while accepting sensitivity of 68%, thereby minimizing false alarms that lead to unnecessary investigations. 4 Lower thresholds (2.5 or 5 µg/L) generate too many false positives without sufficient gain in sensitivity to justify their use. 4