Cancer Antigens

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Related to Cancer Antigens: CA125 ovarian cancer antigen

Cancer Antigens: CA 15-3, CA 19-9, CA 125, and Carcinoembryonic

Synonym/acronym: Carcinoembryonic antigen (CEA), cancer antigen 125 (CA 125), cancer antigen 15-3 (CA 15-3), cancer antigen 19-9 (CA 19-9), cancer antigen 27.29 (CA 27.29).

Common use

To identify the presence of various cancers, such as breast and ovarian, as well as to evaluate the effectiveness of cancer treatment.


Serum (1 mL) collected in a red-top tube. Care must be taken to use the same assay method if serial measurements are to be taken.

Normal findings

(Method: Electrochemiluminometric immunoassay)
Smoking StatusConventional UnitsSI Units (Conventional Units × 1)
SmokerLess than 5.0 ng/mLLess than 5.0 mcg/L
NonsmokerLess than 2.5 ng/mLLess than 2.5 mcg/L
Conventional UnitsSI Units (Conventional Units × 1)
CA 125
Less than 35 units/mLLess than 35 kU/L
CA 15-3
Less than 25 units/mLLess than 25 kU/L
CA 19-9
Less than 35 units/mLLess than 35 kU/L
CA 27.29
Less than 38.6 units/mLLess than 38.6 kU/L


Carcinoembryonic antigen (CEA) is a family of 36 different glycoproteins whose function is believed to be involved in cell adhesion. These structurally related proteins are part of the immunoglobulin superfamily. CEA is normally produced during fetal development and rapid multiplication of epithelial cells, especially those of the digestive system. A small amount of circulating CEA is detectable in the blood of normal adults; normal half-life is 7 days. The liver is the main site for metabolism of CEA. Because of the variability in CEA molecules the test is not diagnostic for any specific disease and is not useful as a screening test for cancer. However, it is very useful for monitoring response to therapy in breast, liver, colon, and gastrointestinal cancer. Serial monitoring is also a useful indicator of recurrence or metastasis in colon or liver carcinoma. CEA levels are higher in the blood of smokers than in non-smokers so most laboratories will have a normal range for each group.

CA 125 or Muc16 is a glycoprotein member of the mucin family and is present in normal endometrial tissue. It appears in the blood when natural endometrial protective barriers are destroyed, as occurs in cancer or endometriosis. CA 125 is most useful in monitoring the progression or recurrence of known ovarian cancer. It is not useful as a screening test because elevations can occur with numerous other conditions such as endometriosis, other diseases of the ovary, menstruation, pregnancy, and uterine fibroids. Persistently rising levels indicate a poor prognosis. Levels may also rise in pancreatic, liver, colon, breast, and lung cancers. Absence of detectable levels of CA 125 does not rule out the presence of tumor.

CA 15-3 monitors patients for recurrence or metastasis of breast carcinoma.

CA 19-9 is a carbohydrate antigen used for post-therapeutic monitoring of patients with gastrointestinal, pancreatic, liver, and colorectal cancer.

CA 27.29 is a glycoprotein product of the muc-1 gene. It is most useful as a serial monitor for response to therapy or recurrence of breast carcinoma.

This procedure is contraindicated for




  • Determine stage of colorectal cancer and test for recurrence or metastasis
  • Monitor response to treatment of breast and gastrointestinal cancers
  • CA 125

  • Assist in the diagnosis of carcinoma of the cervix and endometrium
  • Assist in the diagnosis of ovarian cancer
  • Monitor response to treatment of ovarian cancer
  • CA 15-3 and CA 27.29

  • Monitor recurrent carcinoma of the breast
  • CA 19-9

  • Monitor effectiveness of therapy
  • Monitor gastrointestinal, head and neck, and gynecological carcinomas
  • Predict recurrence of cholangiocarcinoma
  • Predict recurrence of stomach, pancreatic, colorectal, gallbladder, liver, and urothelial carcinomas

Potential diagnosis

Increased in


  • Benign tumors, including benign breast disease
  • Chronic tobacco smoking
  • Cirrhosis
  • Colorectal, pulmonary, gastric, pancreatic, breast, head and neck, esophageal, ovarian, and prostate cancer
  • Inflammatory bowel disease
  • Pancreatitis
  • Radiation therapy (transient)
  • CA 125

  • Breast, colon, endometrial, liver, lung, ovarian, and pancreatic cancer
  • Endometriosis
  • First-trimester pregnancy
  • Menses
  • Ovarian abscess
  • Pelvic inflammatory disease
  • Peritonitis
  • CA 15-3 and CA 27.29

  • Recurrence of breast carcinoma
  • CA 19-9

  • Gastrointestinal, head and neck, and gynecologic carcinomas
  • Recurrence of stomach, pancreatic, colorectal, gallbladder, liver, and urothelial carcinomas
  • Recurrence of cholangiocarcinoma

Decreased in

    Effective therapy or removal of the tumor

Critical findings


Interfering factors


Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in monitoring the progress of various types of disease and evaluate response to therapy.
  • Obtain a history of the patients complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patients gastrointestinal, immune, and reproductive systems, as well as results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patients current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Determine if the patient smokes, because smokers may have false elevations of CEA.
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 minutes. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Recognize anxiety related to test results, and be supportive of perceived loss of independence and fear of shortened life expectancy. Discuss the implications of abnormal test results on the patients lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the American Cancer Association (
  • Reinforce information given by the patients’ HCP regarding further testing, treatment, or referral to another HCP. Decisions regarding the need for and frequency of breast self-examination, mammography, MRI breast, or other cancer screening procedures should be made after consultation between the patient and HCP. The American Cancer Society (ACS) recommends breast examinations be performed every 3 yr for women between the ages of 20 and 39 yr and annually for women over 40 yr of age; annual mammograms should be performed on women 40 yr and older as long as they are in good health. The ACS also recommends annual MRI testing for women at high risk of developing breast cancer. Genetic testing for inherited mutations (BRCA1 and BRCA2) associated with increased risk of developing breast cancer may be ordered for women at risk. The test is performed on a blood specimen. The most current guidelines for breast cancer screening of the general population as well as of individuals with increased risk are available from the American Cancer Society (, the American College of Obstetricians and Gynecologists (ACOG) (, and the American College of Radiology ( Answer any questions or address any concerns voiced by the patient or family.
  • Decisions regarding the need for and frequency of occult blood testing, colonoscopy, or other cancer screening procedures should be made after consultation between the patient and HCP. The American Cancer Society recommends regular screening for colon cancer, beginning at age 50 yr for individuals without identified risk factors. Their recommendations for frequency of screening: annual for occult blood testing (fecal occult blood testing [FOBT] and fecal immunochemical testing [FIT]); every 5 yr for flexible sigmoidoscopy, double contrast barium enema, and CT colonography; and every 10 yr for colonoscopy. There are both advantages and disadvantages to the screening tests that are available today. Methods to use DNA testing of stool are being investigated and awaiting FDA approval. The DNA test is designed to identify abnormal changes in DNA from the cells in the lining of the colon that are normally shed and excreted in stool. The DNA tests under development would use multiple markers to identify colon cancers with various, abnormal DNA changes and would be able to detect precancerous polyps. The most current guidelines for colon cancer screening of the general population as well as of individuals with increased risk are available from the American Cancer Society (, U.S. Preventive Services Task Force (, and the American College of Gastroenterology (
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patients symptoms and other tests performed.

Related Monographs

  • Related tests include barium enema, biopsy breast, biopsy cervical, biopsy intestinal, biopsy liver, capsule endoscopy, colonoscopy, colposcopy, fecal analysis, HCG, liver and spleen scan, MRI breast, MRI liver, mammogram, stereotactic breast biopsy, proctosigmoidoscopy, radiofrequency ablation liver, US abdomen, US breast, and US liver.
  • Refer to the Gastrointestinal, Immune, and Reproductive systems tables at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners
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