What Is a CA-125 Blood Test?
Cancer antigen 125 (CA-125) is a protein found in ovarian cancer
cells. A CA-125 blood test measures the amount of cancer antigen 125 in the
bloodstream. The protein is produced by the cells and can be found in the
A CA-125 blood test may be used to monitor ovarian cancer during
and after treatment. In some cases, it might be used to check for early signs
of ovarian cancer in women who are at a high risk for the disease. However, a
CA-125 blood test isn’t accurate enough to screen for ovarian cancer in all
women because many different conditions can cause abnormal CA-125 levels.
Why Is a CA-125 Blood Test Performed?
A CA-125 blood test is often ordered to monitor the progression
of ovarian cancer. Baseline CA-125 levels are measured before someone undergoes
treatment for ovarian cancer. A drop in CA-125 levels during and after treatment
usually indicates that treatment has been successful. Increases in CA-125
levels following treatment may signify a recurrence of the disease.
After treatment for ovarian cancer, the CA-125 blood test is used
for several years to ensure the disease was treated successfully. It’s
typically ordered every two to four months for the first two years following
the completion of cancer treatment. After this period, the test is ordered
every six months for three years and then once per year.
Some doctors may recommend the CA-125 blood test to women with a
strong family history of ovarian cancer. However, the test usually isn’t used
to screen for ovarian cancer in women who have an average risk of developing
the disease. There are numerous disorders and conditions that can cause
elevated CA-125 levels, such as:
- normal menstruation
- endometrial and fallopian tube cancers
- noncancerous growths in the uterus, such as
- endometriosis, which
is a condition in which the cells of the uterus grow in other areas of the body,
such as the ovaries and the bladder
inflammatory disease, which is a disorder in which the uterus, fallopian
tubes, or ovaries become infected
- cancer of the pancreas
How Is a CA-125 Blood Test Performed?
A CA-125 blood test involves taking a small sample of blood,
typically from a vein in the arm. The following will occur:
- First, a healthcare provider will clean and
disinfect the area with an antiseptic.
- Then, they’ll wrap an elastic band around your
upper arm so your veins swell with blood.
- Once they find a vein, they’ll gently insert the
needle into the vein. They’ll collect the blood in a small tube attached to the
- After enough blood has been drawn, they’ll
remove the needle and cover the puncture site to stop any bleeding.
- The blood sample will then be sent to a
laboratory for analysis.
- Once the laboratory has your results, your
doctor will schedule an appointment to discuss them with you.
What Are the Risks of a CA-125 Blood Test?
A CA-125 blood test is a low-risk procedure. The risks of the
test are common to all blood tests and include:
- difficulty obtaining a blood sample, which
results in multiple needle sticks
- excessive bleeding at the puncture site
- fainting due to blood loss
- infection at the puncture site
What Do My CA-125 Blood Test Results Mean?
CA-125 blood test results can vary depending on the laboratory that
performed the analysis. In most instances, however, CA-125 levels are
considered elevated if they are above 35 units per milliliter.
High levels of CA-125 don’t necessarily confirm the presence of
ovarian cancer or any other type of cancer. CA-125 levels may be elevated due
to another health condition, such as
- uterine fibroids
- pelvic inflammatory disease
Certain cancer medications and surgeries can also alter CA-125
levels. You should discuss your specific results with your doctor to determine
if additional testing is required.
When the CA-125 blood test is being used to monitor the
effectiveness of treatment for ovarian cancer, high levels of CA-125 often
indicate that the cancer isn’t responding to treatment. If this occurs, you may
need to have alternative treatments to combat the disease. A decline in CA-125
levels during treatment indicates that the cancer is responding to treatment.
Some women with ovarian cancer have normal baseline levels of
CA-125, which means they have tumors that aren’t producing the CA-125 protein. If
this happens, a CA-125 blood test won’t help your doctor monitor the
progression of ovarian cancer.