Cancer antigen 15-3 (CA15-3)
Cancer antigen 15-3 (CA15-3) is a protein produced by a variety of cells, particularly breast cancer cells.
Why a CA15-3 test is done
A CA15-3 test may be done to check:
- a person’s response to treatment for breast cancer
- This is the main use of CA15-3 tests.
- if breast cancer has come back (recurred) after treatment
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How a CA 15-3 test is done
A CA15-3 test is usually done in a private laboratory or hospital laboratory. No special preparation is usually needed.
- CA15-3 is usually measured by a blood test.
- The sample is sent to a laboratory to be analyzed by special machines.
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What the results mean
An increased CA15-3 value can occur in non-cancerous and cancerous conditions.
- non-cancerous conditions
- pregnancy
- lactation
- endometriosis
- pelvic inflammatory disease
- benign breast or ovarian disease
- liver diseases such as cirrhosis or hepatitis
- cancerous conditions
- breast cancer
- CA15-3 is often increased in advanced breast cancer or when cancer has spread (metastasized).
- It is rarely increased in women with early stage breast cancer.
- lung cancer
- ovarian cancer
- pancreatic cancer
- liver cancer
- stomach cancer
In cancerous conditions:
- A decrease or return to normal value may mean that the cancer has responded well to treatment.
- An increase may mean that the cancer is not responding well to treatment, is still growing or is coming back (recurring).
- A slight increase may not be significant. The doctor looks at trends in the increase over time.
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What happens if a change or abnormality is found
The doctor will decide if more tests, procedures, follow-up care or additional treatment is needed.
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