Carcinoembryonic Antigen

Carcinoembryonic antigen (CEA), an oncofetal glycoprotein antigen, has been mainly used in the evaluation of patients with adenocarcinomas of the GI tract, especially colorectal cancer. CEA may be elevated in benign as well as malignant diseases (Table 15-10). CEA is not recommended as a screening test for occult cancer (including colorectal) because of its low sensitivity and specificity, but it may be used as supportive evidence in a patient undergoing diagnostic evaluation because of signs and symptoms of colon cancer. Its main value is in monitoring for persistent, metastatic or recurrent colon cancer after surgery. A preoperative elevation should return to normal in 6 to 12 weeks (CEA half-life, 2 weeks), if all disease has been resected. The liver metabolizes CEA, and therefore hepatic diseases can result in delayed clearance. Treatment (surgery, radiation, chemotherapy) may produce

Table 15-9 Causes of Calcium Abnormalities Table 15-10 Conditions Associated with Elevated

Carcinoembryonic Antigen (CEA) Level

Hypercalcemia

Hyperparathyroidism (primary and secondary)

Malignancies: breast, lung, prostate, renal, myeloma, T-cell leukemia, lymphoma

Drugs

Thiazide diuretics

Milk-alkali syndrome Vitamin D intoxication

Granulomatous diseases

Sarcoidosis

Tuberculosis

Chronic renal failure

Immobilization

Hyperthyroidism

Hypocalcemia

Hypomagnesemia

Hypoparathyroidism

Malabsorption of calcium or vitamin D

Acute pancreatitis

Rhabdomyolysis

Hyperphosphatemia

Chronic renal failure

Transfusion of multiple units of citrated blood Drugs

Loop diuretics Phenytoin Phenobarbital

Cisplatin Gentamicin

Pentamidine

Ketoconazole

Calcitonin

Disease

Patients with Elevated CEA (%)

Carcinoma of entodermal origin (colon, stomach, pancreas, lung)

60-75

Colon cancer

Overall

63

Dukes Stage A

20

Dukes Stage B

58

Dukes Stage C

68

Lung cancer

Small cell carcinoma

About 33

Non-small cell carcinoma

About 67

Carcinoma of nonendodermal origin (e.g., head and neck, ovary, thyroid)

50

Breast cancer

Metastatic disease

>50

Localized disease

About 25

Acute nonmalignant inflammatory disease, especially gastrointestinal tract (e.g., ulcerative colitis, regional enteritis, diverticulitis, peptic ulcers, chronic pancreatitis)

Variable

Liver disease (alcoholic cirrhosis, chronic active hepatitis, obstructive jaundice)

Variable

Renal failure, fibrocystic breast disease, hypothyroidism

Variable

Healthy persons

Nonsmokers

3

Smokers

19

Former smokers

7

transient artifactual elevations. CEA has a 97% sensitivity for detecting recurrence in the patient whose postoperative CEA value has returned to normal, and 66% sensitivity for recurrence in the patient with normal preoperative levels.

The adult reference range for CEA is 2.5 ng/mL or less for nonsmokers and 5.0 ng/mL or less for smokers. The degree of CEA elevation correlates with tumor bulk at diagnosis and therefore with prognosis. Values less than 5 ng/mL before therapy suggest localized disease and favorable prognosis, whereas levels greater than 10 ng/mL suggest extensive disease and a worse prognosis. About 30% of patients with metastatic colon cancer have normal CEA levels. Benign diseases do not usually produce CEA levels greater than 5 to 10 ng/mL. For an individual patient, repeat testing or longitudinal monitoring should be conducted at the same laboratory with the same methods because of variability among assays. A 20% to 25% increase in plasma concentration is considered a significant change. A rising CEA level may detect recurrent disease 2 to 6 months before it is clinically apparent.

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