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.
In many cases, the symptoms can resemble a common cold or flu, which sometimes delays diagnosis. Due to these milder symptoms, the infection is also called "walking pneumonia." Despite this, the infection can lead to serious complications if not treated, such as pneumonia, encephalitis, or myocarditis, making prompt and accurate diagnosis crucial to ensure proper treatment.
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 test results can vary by up to 15–25% due to sampling variation, methodological errors, and individual variations. Only changes of 50% or more are considered clinically significant; smaller changes should be confirmed with repeat testing and interpreted with caution. Since different laboratories may use different test methods, results from different places may be difficult to compare directly. This is important to consider when patients are referred between different hospitals or laboratories.
Elevated CA 125 values can be due to several benign conditions such as menstruation, pregnancy, endometriosis, inflammatory diseases in the abdominal cavity, benign cysts, as well as conditions with fluid accumulation like ascites, pleural effusion, or pericardial effusion. Elevated levels can also be seen after major abdominal surgery. Therefore, careful clinical evaluation is required when interpreting the results, and small changes should always be critically assessed.
Reference Range:
- < 35 kU/L
This means that CA 125 values under 35 kU/L are considered within the normal range. Values above this may indicate the need for further investigation but must always be interpreted in conjunction with clinical findings and any symptoms.
