What is the next step for a patient with a history of stage I colon cancer and Lynch syndrome, with rising CA 19-9 (Cancer Antigen 19-9) levels?

Management of Rising CA 19-9 in a Patient with Stage I Colon Cancer and Lynch Syndrome

For a patient with Lynch syndrome, stage I colon cancer history, and rising CA 19-9 levels, the next step should be a comprehensive evaluation including abdominal/pelvic CT scan and referral to a gastroenterologist or hepatobiliary specialist for further assessment.

Understanding the Clinical Scenario

This patient presents with several important features:

• History of stage I colon cancer (surgical resection in 2014)
• Confirmed Lynch syndrome mutation
• Multiple negative surveillance studies through 2023
• Rising CA 19-9 levels: 37 → 53 → 56 U/ml (normal <37 U/ml)

Significance of Rising CA 19-9 Levels

CA 19-9 is a tumor-associated antigen primarily used for:

• Diagnosis in symptomatic patients
• Monitoring therapy response
• Not recommended for screening due to inadequate sensitivity/specificity 1

While the patient's CA 19-9 levels are only modestly elevated, the consistent rising pattern over time is concerning and warrants investigation, even with previously negative imaging 1.

Important Considerations

1. Lynch syndrome context: Patients with Lynch syndrome have increased risk for multiple malignancies beyond colorectal cancer

2. False positives: CA 19-9 can be elevated in various benign conditions:

   • Cholestatic jaundice 2
   • Benign biliary strictures 2
   • Interstitial lung diseases 3
   • Hepatobiliary diseases 4
   • Inflammatory conditions 4

3. Diagnostic yield: About 15% of asymptomatic patients with elevated CA 19-9 may have intra-abdominal malignancies 5

Recommended Approach

1. Imaging studies:

   • Abdominal/pelvic CT scan (sensitivity of 94.1% for detecting malignancies causing elevated CA 19-9) 5
   • Consider MRI/MRCP if biliary pathology is suspected

2. Specialist referral:

   • Gastroenterology or hepatobiliary specialist consultation 1
   • Consider oncology referral if imaging reveals suspicious findings

3. Additional testing based on imaging results:

   • If imaging positive: Further targeted evaluation based on findings
   • If imaging negative: Continue monitoring CA 19-9 levels every 3-6 months with repeat imaging if levels continue to increase 1

Interpretation of Results

• CA 19-9 ≥129 U/ml with suspicious imaging: Immediate referral to hepatobiliary surgeon/oncologist 1
• CA 19-9 <129 U/ml (as in this case) with negative imaging: Continue monitoring 1

Pitfalls to Avoid

1. Overreaction to modest elevations: While the patient's CA 19-9 levels are rising, they remain only moderately elevated. Benign conditions can cause similar elevations 2, 4.

2. Ignoring the trend: The consistent rise in CA 19-9, even if modest, should not be dismissed, particularly in a patient with Lynch syndrome 1.

3. Relying solely on CA 19-9: This marker should always be interpreted alongside imaging findings and clinical context 1.

4. Neglecting Lynch syndrome implications: This genetic condition increases risk for multiple malignancies beyond colorectal cancer, warranting thorough evaluation.