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Cancer antigen 125 (CA125)
Cancer antigen 125 (CA125) is a protein produced by a variety of cells, particularly ovarian cancer cells. It is found in trace amounts in the pleura, pericardium and peritoneum of healthy adults.
A CA125 test may be done to:
- check a person’s response to treatment for ovarian cancer
- This is the main use of CA125 tests.
- check if ovarian cancer has come back (recurred) after treatment
This test is not currently used as a screening test for ovarian cancer because:
- CA125 is not higher than normal in many women with early stage ovarian cancer.
- CA125 may be higher than normal in benign diseases and cancers other than ovarian cancer, so it is not specific to ovarian cancer.
A CA125 test is usually done in a private laboratory or hospital laboratory. No special preparation is usually needed.
- CA125 is usually measured by a blood test.
- The sample is sent to a laboratory to be analyzed by special machines.
An increased CA125 value can occur in non-cancerous and cancerous conditions.
- non-cancerous conditions
- pelvic inflammatory disease
- ovarian cysts
- inflammation of the pancreas (pancreatitis)
- liver diseases such as cirrhosis or hepatitis
- inflammation of the tissue surrounding the lungs (pleura)
- cancerous conditions
- ovarian cancer
- uterine cancer
- cervical cancer
- breast cancer
- lung cancer
- stomach cancer
- colorectal cancer
- pancreatic cancer
- liver cancer
In cancerous conditions:
- A decrease in, or return to normal values of, CA125 may mean that the cancer has responded well to treatment.
- An increase in CA125 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.
The doctor will decide if more tests, procedures, follow-up care or additional treatment is needed.
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For cancer survivors, the Canadian Cancer Society provides a unique opportunity to celebrate their courage in the fight against cancer. During hundreds of Relay For Life events across the country, thousands of survivors join together for the Survivors’ Victory Lap.