What does a CA (Cancer Antigen) 125 level of 174 indicate?

CA-125 Level of 174 U/mL: Clinical Interpretation and Management

A CA-125 level of 174 U/mL is elevated above the standard threshold of 35 U/mL and requires further evaluation with imaging (CT or transvaginal ultrasound with Doppler) to assess for ovarian malignancy, though this level can occur in both benign and malignant conditions. 1

Understanding the Significance of This Level

Malignancy Risk Assessment

• CA-125 has 98.5% specificity for ovarian cancer in women over 50 years when elevated above 35 U/mL, making this level concerning enough to warrant thorough investigation 2
• However, CA-125 detects only 50% of stage I ovarian cancers, so sensitivity for early disease is limited 2
• The level of 174 U/mL falls in an intermediate range where both benign and malignant conditions are possible 3, 4
• Epithelial ovarian cancer is present in approximately 85% of patients with advanced disease who have elevated CA-125, but only 50% of early-stage cases show elevation 5

Benign Conditions That Can Cause This Level

CA-125 levels can exceed 1,000 U/mL in benign conditions, so a level of 174 U/mL does not automatically indicate malignancy 6, 3:

• Endometriosis and adenomyosis are common causes of moderate CA-125 elevation 7, 6, 8
• Pelvic inflammatory disease can elevate CA-125 2, 7
• Benign ovarian cysts (particularly complex cysts with septations) 2, 7
• Menstruation and pregnancy (physiologic elevations) 8, 9
• Ascites from any cause (including cirrhosis) elevates CA-125, even in men 7
• Pleural effusion or peritonitis 3

Immediate Next Steps

Required Imaging Evaluation

Obtain CT scan of abdomen and pelvis with contrast OR transvaginal ultrasound with color/power Doppler to characterize any pelvic masses 1:

• Look for complex ovarian masses with solid and cystic components, internal echoes, septations, papillary projections, ascites, or peritoneal metastases 2
• Color or power Doppler is essential to differentiate true solid components from debris and assess vascular patterns 2
• MRI with IV contrast is superior to CT for characterizing indeterminate adnexal masses if ultrasound findings are unclear 2

Additional Laboratory Testing

Measure CEA and CA 19-9 in addition to CA-125 to help distinguish primary ovarian tumors from gastrointestinal metastases 5:

• A CA-125/CEA ratio >25 favors ovarian origin over gastrointestinal origin 5
• If CEA or CA 19-9 is elevated, consider endoscopy to exclude gastrointestinal primary malignancy 5
• In young women, measure alpha-fetoprotein and beta-HCG to exclude germ cell tumors 1

Interpretation Based on Clinical Context

Postmenopausal Women

• Any persistent ovarian mass in postmenopausal women warrants closer evaluation, as functional cysts should not occur after menopause 2
• Small cysts (<5 cm) with normal CA-125 have significantly lower malignancy risk, but a CA-125 of 174 U/mL changes this assessment 2
• Surgical evaluation is typically indicated for postmenopausal women with elevated CA-125 and ovarian masses 2

Premenopausal Women

• Consider menstrual cycle timing, as CA-125 can be elevated during menstruation 8, 9
• Endometriosis is a common cause of moderate CA-125 elevation in this population 7, 6
• Repeat CA-125 in 2-3 weeks if initial imaging is negative to confirm persistence and calculate rate of progression 1

Monitoring Strategy If Imaging Is Negative

If imaging shows no evidence of malignancy but CA-125 remains elevated 1:

• Repeat CA-125 in 2-3 weeks to confirm the increase and calculate doubling time 1
• Progressive elevation over time, even within normal range initially, warrants further evaluation 2
• Use the same laboratory and test method for all serial measurements to ensure consistency 1
• Median time from CA-125 elevation to clinical relapse is 2-6 months in patients with prior ovarian cancer 1

Critical Caveats

Limitations of CA-125

• CA-125 alone cannot differentiate benign from malignant disease due to high false-positive rates 3, 4
• Mucinous ovarian carcinomas show low CA-125 positivity (only 16%), so normal levels don't exclude this histology 9
• No correlation exists between CA-125 level and clinical stage (FIGO) in ovarian cancer patients 9

When to Suspect Malignancy

High-risk imaging features that increase concern for malignancy 2:

• Solid components >7 mm
• Papillary projections
• Thick septations (>3 mm)
• Abnormal vascular patterns on Doppler
• Ascites or peritoneal implants
• Bilateral complex masses

The combination of elevated CA-125 AND concerning imaging features significantly increases malignancy risk and mandates surgical evaluation 1