What are the chances of ovarian cancer with an elevated inhibin B (Inhibin B) level and a negative Cancer Antigen 125 (CA 125) result?

Elevated Inhibin B with Negative CA-125: Ovarian Cancer Risk Assessment

An elevated inhibin B level of 1200 with a negative CA-125 result indicates a significant risk of mucinous ovarian carcinoma, which requires immediate gynecologic oncology evaluation and imaging studies. While CA-125 is frequently elevated in ovarian cancer, it has poor sensitivity for mucinous subtypes, which are more likely to express inhibin B.

Understanding Tumor Markers in Ovarian Cancer

• CA-125 is elevated in approximately 85% of advanced epithelial ovarian cancers but only about 50% of early-stage cases 1
• CA-125 has poor sensitivity specifically for mucinous ovarian carcinomas, with only 16% showing elevated levels 2
• Inhibin is an ovarian hormone that inhibits follicle-stimulating hormone (FSH) secretion and is elevated in specific ovarian tumor types 3
• Approximately 82% of women with mucinous ovarian carcinomas have elevated serum inhibin concentrations, making it a valuable marker for this specific subtype 3

Diagnostic Approach for Elevated Inhibin B

• Immediate referral to a gynecologic oncologist is recommended for comprehensive evaluation 4

• Comprehensive imaging should include:

  • CT scan of abdomen and pelvis as the first-line imaging study 5
  • Abdominal ultrasound as a complementary study, especially for evaluating parenchymal hepatic or splenic metastases 5
  • MRI if there is concern about diaphragmatic involvement 5

• Laboratory evaluation should include:

  • CA-125/CEA ratio (>25 favors ovarian origin over gastrointestinal origin) 1
  • Additional tumor markers including CEA and CA 19-9 to help distinguish primary ovarian tumors from gastrointestinal metastases 1

Clinical Significance of Marker Patterns

• The pattern of elevated inhibin B with normal CA-125 strongly suggests mucinous ovarian carcinoma 3
• Mucinous carcinomas account for only 3-4% of epithelial ovarian cancers but have distinct biological behavior and marker expression patterns 1
• Serum inhibin levels typically fall after tumor removal, making it useful for monitoring treatment response 3

Management Considerations

• If ovarian cancer is confirmed, primary cytoreductive surgery followed by platinum-based combination chemotherapy is the standard approach 4
• The goal of surgery should be complete resection with no visible residual disease 4
• Standard chemotherapy consists of carboplatin plus paclitaxel for 6 cycles 4

Important Caveats

• False positive inhibin B results can occur with:
  • Benign ovarian conditions (27% of cases) 3
  • Non-ovarian pelvic cancers (7% of cases) 3
• CA-125 has poor specificity and can be elevated in numerous benign conditions including endometriosis, pelvic inflammatory disease, ovarian cysts, and cirrhosis 1, 6
• The specificity of CA-125 for ovarian cancer increases with concentrations >1000 kU/liter 6

Follow-up Recommendations

• If ovarian cancer is diagnosed and treated, follow-up should include:
  • Clinical examinations every 3 months for 2 years, every 4 months during the third year, and every 6 months during years 4 and 5 5
  • Measurement of tumor markers (including inhibin B if initially elevated) at each follow-up 5
  • Imaging studies only if clinically indicated or if tumor markers rise 5