A CA-125 test measures the amount of the cancer antigen 125 (CA-125) in a person’s blood. CA-125 is a protein that is a biomarker or tumor marker. It is found in greater concentration in cancer cells, particularly ovarian cancer cells.
Cancer types that can cause higher than normal levels of CA-125 include:
The CA-125 test helps doctors:
- Monitor ovarian cancer and other cancers to determine if they are responding to treatment
- Monitor patients with ovarian and other cancers post-treatment to check for cancer recurrence
- To an extent, screen for ovarian cancer in women who are at high risk for developing the disease
For the test, a nurse or other clinician obtains a sample of the patient’s blood. A sample of fluid taken from the chest or abdomen can be used instead of the blood. The sample is sent to a laboratory for analysis to determine if the level of CA-125 is abnormal.
Normal levels of CA-125 tend to be less than 35 units per milliliter, but laboratories do vary with what they consider a normal range.
Patients who have previously treated for ovarian cancer that have elevated CA-125 levels may have a cancer recurrence. However, additional testing and surgery (in some cases) is necessary to confirm a recurrence.
It’s important to note, conditions other than cancer can cause higher levels of CA-125, including:
- Uterine fibroids
- Liver disease
- Pelvic inflammatory disease
- The first trimester of a pregnancy
Additionally, cancer medications, recent abdominal surgery or radioactive scans can alter CA-125 levels.