Significance of CA-125 in Mucinous Tumors
CA-125 has limited utility in mucinous ovarian tumors, with only 16% showing elevation compared to 89% positivity in serous ovarian carcinomas. 1
Diagnostic Value of CA-125 in Mucinous Tumors
- CA-125 is less reliable as a tumor marker for mucinous ovarian tumors compared to other epithelial ovarian cancer subtypes 2, 1
- While CA-125 is elevated in approximately 85% of patients with advanced epithelial ovarian cancer overall, mucinous carcinomas (which represent only 3-4% of epithelial ovarian cancers) show significantly lower rates of CA-125 elevation 2, 3
- Studies have demonstrated that mucinous ovarian carcinomas have markedly low CA-125 positivity (16%) compared to serous cystadenocarcinomas (89%) 1
Alternative Markers for Mucinous Tumors
- For mucinous carcinomas (MC), measuring serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9) in addition to CA-125 is recommended to help distinguish primary mucinous ovarian tumors from gastrointestinal metastases 2
- When evaluating mucinous ovarian tumors, endoscopy should be considered if either CEA or CA 19-9 is elevated, especially if the CA-125/CEA ratio is less than 25:1 2
- Recent research indicates that using CA-125 and CA 19-9 together provides better diagnostic accuracy for mucinous ovarian cancer than either marker alone, with combined use increasing sensitivity by 16.7% compared to using only one marker 4
Clinical Implications
- CA-125 provides the highest diagnostic performance (area under ROC curve of 0.745) among tumor markers to differentiate between benign, borderline, and malignant mucinous ovarian tumors, despite its limited sensitivity 5
- Preoperative elevation of serum CA-125, CA 19-9, CEA, and tumor size are useful predictors to differentiate between benign, borderline, and malignant mucinous ovarian tumors 5
- When mucinous histology is suspected or confirmed, clinicians should not rely solely on CA-125 for diagnosis or monitoring due to its limited sensitivity in this subtype 1, 6
Monitoring Disease Progression
- Despite lower sensitivity in initial diagnosis, serial CA-125 measurements may still have value in monitoring disease progression in mucinous tumors that do express this marker 6, 7
- Rising CA-125 levels correlate with disease progression in 92% of ovarian cancer cases across histological types, including mucinous tumors that initially express the marker 7
- CA-125 can increase before clinical progression with a median lead time of 3 months, potentially allowing earlier detection of recurrence 7
Important Caveats
- False-positive CA-125 elevations can occur with benign conditions such as endometriosis, pelvic inflammatory disease, ovarian cysts, and other non-gynecological conditions 2, 3, 8
- Ultrasound-based diagnostic models (IOTA Simple Rules or IOTA ADNEX model) are superior to CA-125 alone in distinguishing between benign and malignant ovarian tumors 2
- A normal CA-125 level does not exclude the presence of disease, particularly in mucinous tumors where the marker has limited sensitivity 1, 7