What laboratory tests should be run for a patient with suspected pancreatic cancer?

Laboratory Tests for Suspected Pancreatic Cancer

CA 19-9 is the most important laboratory test to run when pancreatic cancer is suspected, though it should be accompanied by liver function tests and other supportive laboratory studies. 1

Primary Laboratory Tests

CA 19-9

• Most extensively studied and clinically useful biomarker for pancreatic cancer 2, 1
• Sensitivity of 79-81% and specificity of 80-90% for diagnosis in symptomatic patients 3
• Should be measured before biliary decompression when possible 1
• Important limitations:
  • False negatives in Lewis-negative individuals (5-10% of population) who cannot produce CA 19-9 2, 4
  • False positives with benign biliary obstruction, chronic pancreatitis, cholangitis, and other GI cancers 2, 3
  • Poor screening tool in asymptomatic populations (positive predictive value only 0.9%) 5

Liver Function Tests

• Essential to assess for biliary obstruction 1
• Include:
  • Total and direct bilirubin
  • AST/ALT (transaminases)
  • Alkaline phosphatase
  • Gamma-glutamyl transferase (GGT)

Supportive Laboratory Tests

Complete Blood Count (CBC)

• Evaluates for anemia, which may indicate chronic disease or GI bleeding 1
• Assesses white blood cell count for inflammatory response

Glucose Testing

• Fasting glucose or HbA1c should be checked 2
• New-onset diabetes without risk factors may be an early sign of pancreatic cancer 1
• Emergence of new-onset diabetes in high-risk individuals should prompt additional investigation 2

Additional Tumor Markers

• CEA (Carcinoembryonic Antigen)
  • Can be elevated in pancreatic cancer
  • May be more robust predictor of advanced disease than CA 19-9 6
  • Optimal cut-off value of 7.0 ng/ml for predicting advanced disease 6
• CA 125
  • Consider when CA 19-9 is negative, especially in Lewis-negative patients 4

Other Recommended Tests

• Serum calcium level 1
• Triglyceride levels 1
• Specific hormone levels if neuroendocrine tumor is suspected 1

Clinical Utility of CA 19-9

Diagnostic Value

• Not recommended for screening asymptomatic individuals 2, 5
• Valuable in symptomatic patients with suspected pancreatic cancer 7
• Should be measured after biliary decompression is complete to avoid false positives 2

Prognostic Value

• Levels >100 U/ml may suggest unresectable or metastatic disease 3
• Levels <100 U/ml imply likely resectable disease 3
• Normal preoperative levels (<37 U/ml) correlate with better survival 3

Treatment Monitoring

• Baseline measurement important for monitoring treatment response 1
• Normalization or decrease by ≥20-50% after surgery or chemotherapy associated with better survival 3
• Should be measured after surgery and before adjuvant therapy 2

Important Caveats

• A negative CA 19-9 does not rule out pancreatic cancer, especially in Lewis-negative individuals 4
• Elevated CA 19-9 requires clinical correlation and imaging studies for proper interpretation 1
• CA 19-9 should be interpreted in conjunction with imaging findings, not as a standalone test 1
• Repeat testing may be necessary if initial results are inconclusive but clinical suspicion remains high 1

Remember that laboratory tests are only part of the diagnostic workup. Imaging studies (particularly pancreatic protocol CT and/or MRI/MRCP) and tissue diagnosis via EUS-guided FNA are crucial components in the evaluation of suspected pancreatic cancer 1.