CA 125 Test

What is CA 125?

CA 125 or cancer antigen 125 is a glycoprotein found in the bloodstream. It is produced by cells lining the body wall and abdominal organs, such as organs of the female reproductive system (e.g., the ovaries, fallopian tubes and endometrium) and the peritoneum, often when they are inflamed and stressed. CA 125 is found on the surface of cancer cells and is shed into the blood.

CA 125 is used as a biomarker because, when levels are high, it can indicate cancer or a benign health condition. It is mainly used as a biomarker for ovarian cancer, where CA 125 levels are raised in half of women with early-stage tumours (stages I and II) and 92% of women with advanced-stage tumours (stages III and IV).

CA 125 may also be a sign of other advanced adenocarcinomas (cancers originating in gland cells) and other non-ovarian cancers, such as cancer of the pancreas, lung, liver, uterus, gastrointestinal tract and kidneys.

However, CA 125 may also be associated with non-malignant conditions, including pelvic tumours, endometriosis, inflammatory pelvic disease, acute pancreatitis, cirrhosis, peritonitis, ascites and inflammatory bowel disease, and normal physiological conditions, such as ovulation, menstruation, and pregnancy.

What is a CA 125 test?

The CA 125 test measures the amount of CA 125 in the blood.

While CA125 is used as the main ovarian cancer marker, results can be misleading; false positives and false negatives can occur:

• False positive: High CA 125 level but no ovarian cancer. CA 125 is produced by non-cancerous conditions of certain other tissues (e.g., endometriosis, uterine fibroids, and pelvic inflammatory disease), and normal physiological conditions (e.g., during the menstrual cycle and pregnancy).
• False negative: Low CA 125 level but ovarian cancer present. Around 20% of ovarian tumours do not make CA 125, CA-125 levels may be low in early-stage cancer, and CA 125 concentrations may not depend on the cancer stage (an advanced-stage cancer may not produce more CA 125 than an early-stage cancer).

Why is a CA 125 test important?

In cases of suspected or confirmed ovarian cancer, the CA-125 blood test can help in:

• Detection: The test is used to gather information about a mass in the abdomen that could be ovarian cancer. The test does not detect ovarian cancer.
• Diagnosis: CA 125 test may be used together with other diagnostic investigations if ovarian cancer is suspected or there are symptoms of ovarian cancer. The test does not diagnose ovarian cancer, diagnosis requires a biopsy.
• Management: To monitor treatment over time as regular CA 125 testing can indicate whether the treatment is working or not. Once treatment is completed, this test may also be used for routine surveillance to ensure that the cancer has not come back. The test may also be used to monitor certain other types of cancer, particularly during and after treatment.
• Screening: The test is used in women at high-risk of ovarian cancer, such as if a woman has a gene mutation or variant that increases the risk of the cancer or has a family history of ovarian cancer. However, the CA 125 test is too unreliable to be a general screening tool for ovarian cancer in women at average risk, or with no risk factors or symptoms.

Who should have their CA 125 level tested?

The CA 125 test can be used in women with:

• A diagnosis of ovarian cancer and are receiving treatment (to check the cancer is regressing).
• A history of ovarian cancer and have finished treatment (to check the cancer has not returned).
• A high risk of developing ovarian cancer. This includes women (1) with a close relative (mother, sister) or two or more other relatives who have had ovarian cancer; (2) who have had cancer of the breast, uterus, or colorectum, or with a family member who have had either cancer of the breast or colorectum; and (3) who have a specific genetic change that increases the risk of ovarian cancer, such as a mutation in the BRCA1 and BRAC2 genes or a genetic disorder like Lynch syndrome.
• A mass (lump) in the abdomen that could be ovarian cancer. The test is one of the assessments used to investigate the possibility of ovarian cancer.
• Persistent symptoms that suggest ovarian cancer and should be investigated, such as pelvic and abdominal pain, distension or bloating, loss of appetite and feeling uncomfortably full after eating little, and an increased need to urinate and with sudden urgency.

How to test for CA 125?

The CA 125 test measures the level of Ca 125 in the blood. The Online Clinic can provide you with a specially-designed easy-to-use test kit containing all you need to perform a finger-prick blood test at home. It only requires a few drops of blood. Blood samples are then sent to a laboratory for analysis in a reply-paid envelope that is included with the kit. Otherwise, a blood sample can be collected by a healthcare professional from a vein in your arm at a clinic or pharmacy. All test results are then sent to a doctor at The Online Clinic who will explain the findings to you.

How long do results for the CA 125 take?

The CA 125 test results are back in 1 day of your sample being booked in at the lab.

References

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