Imperial Collage Healthcare

Cancer antigen 15-3 (CA 15-3)

Test Background
CA 15-3 is a high molecular weight (300-450 kDa) transmembrane glycoprotein encoded by the MUC1 gene. It is defined by reactivity with 2 monoclonal antibodies, DF3 and 115D8. CA 15-3 is expressed predominantly in breast cancer (raised in 30 % of localised disease, 75 % metastatic), though primary tumours of the lung, colon, pancreas, liver and endometrium may also give rise to elevations of CA 15-3. Elevations of CA 15-3 values have been reported in individuals with non-malignant conditions such as cirrhosis, hepatitis, autoimmune disorders and benign diseases of the ovary and breast. While increasing CA 15-3 can be the earliest sign of metastatic disease in ~70 % patients, there is little evidence showing that early diagnosis of progressive disease positively impacts survival or quality of life.

Clinical Indications
Breast cancer

  • Diagnosis: since CA 15-3 may be elevated in normal individuals and benign conditions, and there is a low incidence of CA 15-3 elevation in early stage breast cancer, CA 15-3 should not be used for screening.
  • Treatment monitoring: when serum CA 15-3 level is elevated it may be used to monitor response to therapy in combination with imaging and clinical examination. For patients with metastatic disease in whom CA 15-3 is being monitored, the marker should be determined prior to each chemotherapy course and at 3 month intervals.
  • Surveillance: despite the lack of high level evidence, many patients opt to have serial levels of CA 15-3 determined following surgery.

Reference Range
<32 kIU/L

Sample Required
SST (gold top) preferred, serum (red top) accepted

Sample Volume
0.5 mL

Turnaround Time
4 days

Abbott Alinity

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