From the Guidelines
CA 125 is a blood test that measures the level of cancer antigen 125, a protein produced by certain cancerous cells, particularly ovarian cancer cells, and is primarily used to monitor treatment response in women with ovarian cancer and to detect recurrence after treatment, as stated in the study by 1. This test is not recommended as a screening test for ovarian cancer in the general population due to its limited sensitivity and specificity, with false positives being common, and some ovarian cancers may not produce elevated CA 125 levels, as noted in the study by 1. The normal range for CA 125 is generally considered to be less than 35 U/mL, though this can vary between laboratories. Some of the key points to consider when interpreting CA 125 results include:
- CA 125 levels may be elevated in ovarian cancer, but can also increase in other conditions including endometriosis, pelvic inflammatory disease, liver disease, pregnancy, and menstruation, as mentioned in the study by 1.
- The test is most valuable when used to track changes over time in patients with known ovarian cancer, where rising levels may indicate disease progression or recurrence, as stated in the study by 1.
- Interpretation of CA 125 results should always be done by healthcare providers in the context of a patient's complete clinical picture, taking into account symptoms, physical examination, and other diagnostic tests, as recommended in the study by 1. It's also important to note that the role of CA 125 in monitoring recurrence is still being debated, with some studies suggesting that it may not be effective in detecting small tumor deposits, as mentioned in the study by 1. However, the study by 1 provides the most recent and highest quality evidence, and therefore, its findings should be prioritized when making clinical decisions. In terms of surveillance and diagnosis of recurrence, the study by 1 provides guidance on the recommended frequency of CA 125 monitoring and imaging tests, which should be individualized based on the patient's risk of recurrence and overall health status. Overall, CA 125 is a useful tool in the management of ovarian cancer, but its limitations and potential false positives must be carefully considered in the context of each patient's unique clinical situation, as emphasized in the study by 1.
From the Research
CA 125 Overview
- CA 125 is a tumor biomarker used primarily for monitoring ovarian cancer 2
- It is most consistently elevated in epithelial ovarian cancer, but can also be expressed in other gynecologic and non-gynecologic cancers 2
- The CA 125 assay has been used for over four decades as the primary ovarian cancer marker 3
Diagnostic Performance
- The diagnostic performance of CA 125 for detecting ovarian and non-ovarian cancer in primary care has been evaluated, with a sensitivity and specificity of 35 U/ml 4
- A CA 125 value of 53 U/ml equates to a 3% probability of ovarian cancer overall, varying by age 4
- CA 125 is a useful test for ovarian cancer detection in primary care, particularly in women ≥50 years old 4
Prognosis and Therapy
- CA 125 levels can aid in distinguishing malignant from benign pelvic masses and monitoring ovarian cancer treatment response 2, 5
- The rate of decline in CA 125 during primary chemotherapy is an important independent prognostic factor in ovarian cancer 2
- Rising CA 125 values have preceded clinical detection of recurrent disease by at least 3 months in most studies 2
- Combining multiple drug classes, including immune checkpoint inhibitors, anti-VEGF, and PARPi, may improve survival in advanced ovarian cancer 6
Limitations and Future Directions
- The focus on diagnosing ovarian cancer in stages I and II using CA 125 as a diagnostic biomarker has not improved patients' survival 3
- Screening average-risk asymptomatic women with CA 125 is not recommended by any professional society 3
- Future research should focus on improving sensitivity and specificity of CA 125, as well as exploring novel biomarkers and treatment strategies for ovarian cancer 2, 3, 6