CEA Half-Life
The biological half-life of carcinoembryonic antigen (CEA) in serum is approximately 3-7 days in most patients, with a median of 4.4-4.8 days following complete tumor resection. 1, 2
Biological Half-Life Parameters
Normal clearance range: CEA half-life ranges from 1.2 to 88.1 days across different patients, but the median value is consistently 4.4-4.8 days in those without residual disease 1, 2
Post-surgical kinetics: After curative resection of colorectal cancer, CEA should normalize within 4-6 weeks if all tumor tissue has been removed, based on the typical half-life of 3-7 days 1, 2
Failure to normalize: A persistently elevated CEA beyond 4-6 weeks post-resection indicates inadequate tumor removal or occult metastatic disease 3
Prognostic Significance of CEA Half-Life
Prolonged CEA half-life (≥4.8 days) after curative surgery is an independent predictor of poor prognosis and increased recurrence risk. 1, 2
Recurrence Prediction
Patients with recurrent disease have significantly longer mean CEA half-life (11.7 ± 17.9 days) compared to those without recurrence (6.2 ± 4.9 days) 1
Survival outcomes: Patients with CEA half-life <4.8 days demonstrate superior 3-year disease-free survival (87% vs 66%) and overall survival (90% vs 80%) compared to those with longer half-life 2
Independent prognostic factor: Cox regression analysis confirms that CEA half-life is an independent predictor of outcomes, separate from TNM staging 2
Clinical Application
Calculate CEA half-life by measuring preoperative CEA and serial postoperative values (typically at 1,2,4, and 6 weeks) in patients with preoperatively elevated CEA (≥5 ng/mL) 1, 2
High-risk identification: Patients with CEA half-life ≥4.8 days should be considered high-risk and warrant more intensive surveillance protocols 2
Important Clinical Caveats
Spurious Elevations During Treatment
Early chemotherapy effect: CEA levels may show transient increases during the first 4-6 weeks of new chemotherapy, representing tumor lysis rather than progression 4
False response: Approximately 67% of patients (6/9 in one series) showed CEA decline with chemotherapy initiation without true clinical response, making CEA unreliable as a sole indicator of treatment efficacy 5
Comparison to Circulating Tumor Cells
CEA persistence: Unlike circulating tumor cells which have a very short half-life of 1-2.4 hours, CEA persists for days after tumor removal, making it detectable for several weeks post-resection 4
Detection window: This longer half-life provides a practical advantage for monitoring, as CEA remains measurable long enough for serial testing 4
Practical Monitoring Strategy
Baseline establishment: Measure preoperative CEA in all patients with colorectal cancer to establish baseline and determine if marker will be useful for surveillance 4
Early postoperative measurement: Check CEA at 4-6 weeks post-resection; failure to normalize suggests incomplete resection or occult disease 1, 3
Calculate half-life: In patients with preoperative CEA ≥5 ng/mL, calculate actual half-life using serial measurements to stratify recurrence risk 1, 2
Ongoing surveillance: For stage II-III disease, monitor CEA every 3 months for at least 3 years if patient is a surgical or systemic therapy candidate 4