Synonyms

   Cancer Ag 15-3

Clinical Significance

   Managing breast cancer patients when used in conjunction with clinical information and other diagnostic procedures.

   Serial testing to assist in early detection of disease recurrence in previously treated stage II and III breast cancer patients.

   Monitoring response to therapy in metastatic breast cancer patients.

Specimen

   Serum

Stability

   Refrigerated (preferred) : 5 days

   Frozen : 90 days

Reference Range

   < 34.5 U/ml

Interpretation

   In general, higher concentrations of CA 15-3 suggest that the breast cancer is more advanced and that a larger amount of tumour is present. The concentration of CA 15-3 tends to increase as the cancer grows. In metastatic breast cancer (cancer that has spread to other organs), the highest concentrations of CA 15-3 are often seen when the cancer has spread to the bones and/or the liver.

   Mild to moderate elevations of CA 15-3 also are seen in a variety of other conditions, including liver and pancreatic cancer, cirrhosis, and benign breast disorders as well as in a certain percentage of apparently healthy individuals. The CA 15-3 elevations seen in these non-cancerous conditions tend to be stable over time.

   A negative CA 15-3 result (a result below the reference range quoted by the local laboratory) cannot be used to confirm the absence of cancer in a patient. In addition, 25% to 30% of individuals with advanced breast cancer have tumours that do not produce CA 15-3.

Limitation

   Testing for cancer antigen 15-3 (CA 15-3) should be performed in conjunction with other clinical methods used for the early detection of recurrence. In rare cases, interference due to extremely high titers of antibodies to ruthenium or streptavidin can occur.