Cancer Antigen 125 (CA125) Test
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
The cancer antigen 125 (CA-125) test is performed on a blood sample to measure the level of the CA-125 protein, which may be elevated in certain cancers. It is used primarily to monitor treatment and detect recurrence of ovarian cancer and to help assess pelvic masses alongside other clinical information.
Why get tested?
To monitor treatment for ovarian cancer or to investigate for a possible ovarian cancer.
When to get tested?
Before starting therapy for ovarian cancer or if at high risk for developing ovarian cancer, and at intervals during and after treatment. CA 125 may also be request by your GP if you have persistent or frequent symptoms that may be caused by ovarian cancer.
Sample required?
A blood sample taken from a vein in the arm
Test preparation needed?
None
Common questions
CA 125 is mainly used to monitor therapy during treatment for ovarian cancer. CA 125 is also used to detect whether cancer has come back after treatment is complete. This test is sometimes used to follow women who are at high-risk because they have a family history of ovarian cancer but who do not yet have the disease. CA 125 is also recommended together with pelvic ultrasonography in women aged over 50 years who have persistent, continuous or worsening unexplained tummy pain, bloating, feeling full and/or loss of appetite or problems with urination and in whom a doctor is concerned about a possible ovarian cancer after examining the tummy.
Before a patient starts treatment for ovarian cancer, the doctor will measure CA 125 to be able to compare it with future measurements. During therapy, doctors use CA 125 testing, at intervals, to follow the response to therapy. CA 125 may also be measured several times after therapy is completed to catch any early signs of the cancer’s return.CA 125 may also be requested by your GP if you have persistent or frequent symptoms (e.g. unexplained tummy pain, bloating, feeling full and/or loss of appetite or problems with urination) to determine if you require an ultrasound scan of the abdomen and pelvis.
If CA 125 levels fall during therapy, this generally indicates that the cancer is responding to treatment. If CA 125 levels rise, the cancer may not be responding to treatment. High CA 125 levels after treatment is complete may indicate that the cancer has come back. In women without a diagnosis of ovarian cancer a raised CA 125 may indicate the need for an ultrasound of the abdomen and pelvis.
A CA 125 result that is higher than normal does not always mean a patient has ovarian cancer. CA 125 can be high in many normal or benign conditions (for example, pregnancy, menstruation, uterine fibroids, endometriosis and pelvic inflammatory disease). A CA 125 test isn’t accurate enough to use for ovarian cancer screening in the general population, because many noncancerous conditions (such as those described above) can increase the CA 125 result..
No, not all ovarian cancers have increased levels of CA 125. Elevated levels have been found in about 80% of women with ovarian cancer.
No. CA 125 may be elevated in several other conditions and diseases. CA 125 may normally be increased in early pregnancy and during menstruation. It can also be increased in diseases such as pelvic inflammatory disease or endometriosis and sometimes in hepatitis and cirrhosis of the liver.
Family history is a risk factor for ovarian cancer. If you have close family members who have had ovarian cancer, you are at higher risk than someone who has no family history of the disease. Make sure your doctor knows about your family medical history.
If you have a strong family history of ovarian cancer or you have the BRCA1 or BRCA2 gene mutation, your doctor may recommend a CA 125 test as one way to screen for ovarian cancer.