Cancer Antigen 125 (CA125)

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A tumor marker is a substance that can be detected in the blood or other body fluids that researchers have identified as having a correlation to the presence of particular types of cancer. CA125, a substance found in very low levels in the human body, has become a widely used tumor marker for gynecological cancers. Most often CA125 is measured in women with those cancers involving the ovaries, uterus, and fallopian tubes.

CA125 tests are one of a series of indicators that may be used by your doctor to determine if you have cancer, and if it is progressing or not. Others may include your family history, a pelvic exam, sonogram and/or MRIs.

How are levels of CA125 determined?

A blood sample is taken and analyzed. Results are usually available within a few days.

What is a normal CA125 level?

Usually CA125 levels range between 1-35 u/ml, but can vary. It is important that you discuss your CA125 level with your physician to fully understand how to interpret your own results.

What if my CA125 level is elevated? Does it mean I definitely have cancer?

No. If your CA125 level is found to be elevated your doctor will need to rule out other conditions as possible causes. Conditions that can have an impact on CA125 levels include menstruation, pregnancy, ovarian cysts, and peritonitis, (an infection of the lining of the abdomen). In fact, abnormal or elevated CA125 levels may be detected in a small percentage of healthy individuals and patients with nonmalignant conditions.

Nonetheless, an increased level of CA125 may be present 3 to 4 months before a malignant tumor can be detected by other means, therefore, the CA125 test is an important cancer screening device for women considered at increased risk of developing cancer of the reproductive system.

If my CA125 count is low, does that rule out cancer?

Unfortunately, normal levels of CA125 do not definitively rule out the presence or recurrence of cancer. Again, it is combination of tests, observations and feedback that will help your doctor diagnose your condition.

Will my CA125 count tell me if my treatment is working?

CA125 counts can be particularly important once a cancer diagnosis is made, to help determine the effectiveness of treatment. Declining levels of CA125 often represent a positive response to treatment while increasing levels denotes a poor response, but not always. Dependent on the individual being tested, CA125 results can be used by a doctor to continually monitor and improve treatment options.

How frequently should my CA125 levels be evaluated?

The frequency of CA125 monitoring during or after cancer treatment will be influenced by the type of cancer, size of the tumor(s), type of treatment, and the patient's baseline CA125 level. Your doctor should discuss this with you.

What is CA125-II?

An improved version of the original CA125 assay, CA 125-II, is now commercially available.

Online Bibliography

Half the cure is finding the cancer, by Marilyn Linton -- Toronto Sun, September 3, 1999

Oncolink: Cancer Antigen 125, by Karen T. Bruchak, RN, MSN, MBA

Remember to always consult your primary care doctor before trying any new treatment or if you have questions or concerns about the treatment you are receiving!

Additional Online Cancer Resources

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