From the Guidelines
CA-125 is a protein biomarker primarily used to monitor ovarian cancer treatment and detect recurrence, and it is not suitable as a standalone screening test for ovarian cancer in the general population. It's produced by certain cancer cells and released into the bloodstream, where it can be measured through a simple blood test. Normal CA-125 levels are typically below 35 U/mL, though this can vary between laboratories. While CA-125 is most strongly associated with ovarian cancer, elevated levels can also occur with other cancers (endometrial, fallopian tube, lung, breast, and gastrointestinal cancers) and non-cancerous conditions (endometriosis, pelvic inflammatory disease, liver disease, and pregnancy) 1.
Key Points
- CA-125 is not specific to ovarian cancer and can be elevated in other conditions, making it unsuitable for screening the general population.
- The test is most valuable when tracking changes in CA-125 levels over time in patients with known ovarian cancer.
- Rising CA-125 levels may indicate disease progression or recurrence, while falling levels often suggest treatment effectiveness.
- Doctors typically use CA-125 measurements alongside imaging studies and physical examinations for comprehensive patient monitoring 1.
Clinical Use
CA-125 measurements are used to monitor ovarian cancer treatment and detect recurrence. The test is not used as a screening tool for the general population due to its low specificity. In patients with known ovarian cancer, CA-125 levels are used to track disease progression and response to treatment. Imaging studies, such as ultrasound and CT scans, are also used to monitor disease progression and detect recurrence 1.
Limitations
CA-125 has several limitations, including its low specificity and potential for false-positive results. Elevated CA-125 levels can occur in non-cancerous conditions, such as endometriosis and pelvic inflammatory disease. Additionally, CA-125 levels may not be elevated in all cases of ovarian cancer, particularly in early-stage disease 1.
From the Research
Definition of CA 125
- CA 125, also known as mucin 16 or MUC16, is a large membrane glycoprotein belonging to the wide mucin family, encoded by the homonymous MUC16 gene 2.
- It is a high-molecular-mass glycoprotein expressed on the cell surface of some derivatives of embryonic coelomic epithelium 3, 4.
- CA 125 is a coelomic epithelial antigen which is widely used to monitor residual disease in patients undergoing chemotherapy for ovarian cancer 5.
Clinical Use of CA 125
- CA 125 is used as a tumor marker of ovarian cancer, particularly to monitor response to therapy in patients with epithelial ovarian cancer and to detect residual or recurrent disease 2.
- However, due to its limited specificity and sensitivity, CA 125 alone cannot be an ideal biomarker 2.
- The combined use of CA 125 with HE4, another ovarian cancer marker, has been shown to improve clinical performance in identifying epithelial ovarian cancer relapse 2.
- CA 125 levels can also be elevated in benign conditions, such as menstruation, pregnancy, benign pelvic tumors, pelvic inflammatory diseases, ovarian hyperstimulation syndrome, peritonitis, and diseases leading to pleural effusion or ascites 3, 4, 6.
Reference Levels for CA 125
- The generally accepted upper limit of normal for CA 125 is 35 U/mL, but this value may need to be redefined based on the patient's physiologic state 6, 5.
- For normal premenopausal women, the overall upper limit of CA 125 should be 50 U/mL, with stratified values based on menstrual status 6.
- For postmenopausal women, the CA 125 levels should be no more than 35 for those with vaginal bleeding and 20 for those without bleeding 6.
- One study suggests that the normal value for CA 125 used for patient follow-up after treatment for gynecologic adenocarcinoma should be redefined, with an upper limit of normal of 20 U/ml 5.