CA125: Primarily Used for Ovarian Cancer Monitoring and Management
CA125 (Cancer Antigen 125) is primarily used as a tumor marker for monitoring response to treatment, detecting recurrence, and helping differentiate pelvic masses in ovarian cancer, but it has significant limitations as a screening tool due to its lack of sensitivity for early-stage disease and limited specificity.
Primary Uses of CA125
- CA125 is most valuable in monitoring the clinical course of patients with epithelial ovarian cancer during chemotherapy and predicting tumor recurrence in patients who are clinically tumor-free 1
- It serves as an important component in the preoperative evaluation of patients with suspected ovarian carcinoma, though it should not be used alone for diagnosis 1
- CA125 helps assess response to treatment and progression of ovarian cancer when used in combination with radiological and clinical assessment 1
- It can aid in differentiating between benign and malignant pelvic masses, particularly in postmenopausal women 1, 2
Limitations of CA125
- CA125 has poor sensitivity for early-stage ovarian cancer, with only about 50% of stage I ovarian cancer patients showing elevated levels 1
- It lacks specificity as a standalone screening tool due to false-positive results in various benign conditions 1
- False-positive elevations occur with endometriosis, benign ovarian cysts, pregnancy, pelvic inflammatory disease, pancreatic cancer, and cirrhosis 1
- CA125 is not a reliable marker in non-high-grade serous carcinoma (non-HGSC) epithelial ovarian cancer types, particularly in mucinous carcinoma 1
CA125 in Clinical Practice
- The true-positive rate increases to approximately 80% with stage II or greater ovarian cancer 1
- CA125 should be used in combination with other diagnostic modalities, never in isolation 1
- Serial monitoring of CA125 levels can detect recurrent disease before clinical symptoms appear, though the clinical value of this lead time remains unclear 1, 3
- A high CA125/CEA ratio can help differentiate ovarian from gastrointestinal primary tumors 1, 4
Other Important Considerations
- CA125 is the standard against which newer ovarian cancer biomarkers are judged 3, 5
- For improved diagnostic accuracy, CA125 is sometimes used in combination with HE4 (Human Epididymis Protein 4) or within algorithms like ROMA (Risk of Ovarian Malignancy Algorithm) and OVA1 6
- Progressive elevation of CA125 over time, even within normal range, may indicate malignancy and warrants further evaluation 1, 2
- The Gynecologic Cancer InterGroup (GCIG) has established criteria for using CA125 to assess response and progression in ovarian cancer 1
Practical Application
- Normal CA125 values are typically below 35 U/mL, with higher specificity (98.5%) for women over 50 years of age 1
- CA125 monitoring is recommended during follow-up visits for ovarian cancer patients, especially if initially elevated 1
- When elevated CA125 levels are detected during surveillance, imaging studies (CT, MRI, or PET-CT) are indicated to evaluate for recurrence 1
- CA125 may have limited utility with newer targeted therapies, where radiological and clinical assessment should take precedence 1