What is CA 125
CA 125, or cancer antigen 125, is a glycoprotein found on the surface of certain cells and can be measured in the blood. It is a tumor marker primarily used in gynecological oncology to evaluate and monitor the treatment of ovarian cancer. CA 125 is produced by mesothelial cells lining the body's serous cavities, such as the peritoneum, pleura, and pericardium.
Why is the analysis of CA 125 performed?
The analysis of cancer antigen 125 is primarily performed to help detect or monitor ovarian cancer, as CA 125 is a protein that can be present in higher concentrations in cases of ovarian cancer. It is important to note that elevated levels of CA 125 are not specific only to ovarian cancer. CA 125 can also be elevated in other types of cancer and in several non-malignant (benign) conditions.
Other cancers where CA 125 can be elevated:
- Uterine cancer (endometrial cancer)
- Fallopian tube cancer
- Pancreatic cancer
- Breast cancer
- Lung cancer
- Colorectal cancer
- Stomach cancer
Benign conditions where CA 125 can be elevated:
- Endometriosis
- Inflammatory diseases of the pelvis
- Liver cirrhosis
- Pregnancy
- Menstruation
- Peritoneal inflammation (peritonitis)
- Heart failure with fluid accumulation in the abdomen (ascites)
Therefore, CA 125 is not a tumor marker that is specific only for ovarian cancer. Elevated levels can occur in several different cancer types and also in non-malignant conditions. Therefore, the CA 125 analysis should be interpreted in combination with other clinical findings and diagnostic tests. By measuring the concentration of CA 125, the doctor can obtain important information that can be used as part of the diagnostic process, such as:
- Identify risk for ovarian cancer: If a woman has symptoms such as abdominal pain, bloating, or changes in menstrual patterns, a CA 125 test can help determine if further investigations are needed.
- Monitor treatment effectiveness: During and after treatment for ovarian cancer, CA 125 levels are measured regularly to see how well the treatment is working. If levels decrease, it often indicates that the treatment is effective.
- Detect recurrence early: If CA 125 levels begin to rise again after completing treatment, it may be an early sign that the cancer has returned.
It is important to note that elevated CA 125 levels do not always mean that one has cancer. Levels can also be elevated in other conditions such as:
- Benign ovarian cysts
- Endometriosis
- Pregnancy
- Menstruation
Therefore, the CA 125 test is often used in conjunction with other examinations, such as ultrasound or imaging studies, to provide a more complete picture of health status. The test is a valuable tool for doctors to make informed decisions regarding diagnosis and treatment.
Interpretation of Test Results and Reference Values
CA 125 results may be affected by biological variation, sample collection, and the analytical method used. Small differences between repeated measurements should therefore be interpreted with caution. Because laboratories may use different analytical methods, follow-up samples should, whenever possible, be analyzed using the same method and by the same laboratory.
An elevated CA 125 level should always be clinically assessed and, when appropriate, further investigated based on the patient’s symptoms, clinical findings, and other test results. CA 125 is not a cancer-specific marker, and an elevated level does not necessarily indicate cancer. Elevated levels may also occur with several benign conditions, including menstruation, pregnancy, endometriosis, inflammation in the abdominal cavity, and benign cysts. CA 125 may also be elevated in conditions involving fluid accumulation, such as ascites, pleural effusion, or pericardial effusion, as well as after major abdominal surgery.
When testing is repeated, changes over time may provide important information. However, changes of less than 50% may also be clinically relevant. Results should therefore not be evaluated solely on the basis of a specific percentage change but should always be interpreted within the overall clinical context.
Reference Range:
- < 35 kU/L
A value above the laboratory’s reference limit may indicate a need for further evaluation. However, a value within the reference range does not rule out disease. The applicable reference range may vary depending on the laboratory and analytical method and is provided in the laboratory report.
