Cancer Antigen 15-3, (CA 15-3)
1 SST/2.0 mL serum. After 30 minutes of clotting, promptly centrifuge and refrigerate.
Frozen serum if testing cannot be performed within 24 hours.
Refrigerated 24 hours; Frozen 7 days
Elevated serum CA 15-3 concentrations are found in 5% of stage I, 29% of stage II, 32% of stage III and 95% of stage IV carcinoma of the breast. Most (96%) patients with a CA 15-3 increase of greater than 25% have disease progression. Most (nearly 100%) patients with a CA 15-3 decrease of greater than 50% are responding to treatment.