Cancer Antigen 15-3 (CA 153)

General Information

Carbohydrate Antigen (CA) 15-3 is a high molecular weight (250-500 kDa) transmembrane glycoprotein of the mucin family and it is encoded by the MUC1 gene.  It is defined by reactivity with two monoclonal antibodies (DF3 and 115D8) in an immunometric assay.  Its exact function is unknown but it is thought to have a role as a lubricant and in cell adhesion.  CA15-3 is found on the cell surfaces in the gastrointestinal, respiratory and reproductive tracts and in the breast, and in low concentrations in the serum of healthy adults.  Serum concentrations are similar in men and women, and pregnancy, lactation and menopause do not appear to alter serum CA15-3 concentrations significantly.  The half-life of CA15-3 in serum is unknown.

CA15-3 is mainly used as a marker of breast cancer. Preoperative CA15-3 concentrations are only elevated in 30-40% of patients with primary breast cancers, although the proportion of patients with elevated values tend to increase with stage or size of the primary tumour.  This means that CA15-3 has no role to play in the screening or diagnosis of breast cancer.  In contrast, more than 70% of patients with distant metastasis have elevated marker concentrations.  Concentrations can be particularly elevated when either bone or liver metastasis is present.  Post-operative concentrations are a strong prognostic indicator.

CA15-3 is not organ-specific and serum concentrations may be elevated in the following malignancies: colorectal cancer, ovarian carcinoma, lung cancer and pancreatic cancer. Therefore, serum CA15-3 measurement alone is of little use in identifying unknown primary cancers in patients with undifferentiated metastases.

Serum CA15-3 concentrations may be elevated in the following benign conditions: hepatitis, liver cirrhosis, benign diseases of the ovaries, lungs and breasts. CA15-3 is removed from circulation by the liver, so chronic liver disease, particularly with ascites, may cause elevated serum concentrations. Elevated serum CA15-3 concentrations are not absolute evidence of the presence of malignant disease, and should be used in conjunction with other diagnostic and clinical information.

Patient Preparation

No special patient requirements. Serum assay only/ Blood must be collected into a yellow/red top vacutainer.

Notes

Reference Range

<31.3 KU/L