CA15-3 is a tumor marker

Tumor marker

A tumor marker is a substance found in the blood, urine, or body tissues that can be elevated in cancer, among other tissue types. There are many different tumor markers, each indicative of a particular disease process, and they are used in oncology to help detect the presence of cancer...

 used to monitor certain cancers, especially breast cancer

Breast cancer

Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

. It is found on the surface of many types of cancer cells and shed into the blood stream. It is used to monitor advanced, ie metastatic, cancer.

Elevated CA15-3, in conjunction with alkaline phosphatase

Alkaline phosphatase

Alkaline phosphatase is a hydrolase enzyme responsible for removing phosphate groups from many types of molecules, including nucleotides, proteins, and alkaloids. The process of removing the phosphate group is called dephosphorylation...

 (ALP), was found to be associated with an increased chance of early recurrence in breast cancer

Breast cancer

Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

.

See also

• Breast cancer treatment
  Breast cancer treatment
  The mainstay of breast cancer treatment is surgery when the tumor is localized, followed by chemotherapy , radiotherapy and adjuvant hormonal therapy for ER positive tumours . Management of breast cancer is undertaken by a multidisciplinary team based on national and international guidelines...
  
  
• carcinoembryonic antigen
  Carcinoembryonic antigen
  Carcinoembryonic antigen is a glycoprotein involved in cell adhesion. It is normally produced during fetal development, but the production of CEA stops before birth. Therefore, it is not usually present in the blood of healthy adults, although levels are raised in heavy smokers...
  
  (CEA), another marker used for cancer