Is there a blood test for pancreatic cancer, such as a Carbohydrate Antigen 19-9 (CA 19-9) test?

Blood Tests for Pancreatic Cancer

CA 19-9 is available as a blood test for pancreatic cancer, but it is not recommended for screening due to inadequate sensitivity and specificity for accurate diagnosis. 1

CA 19-9 as a Tumor Marker

• CA 19-9 is a tumor-associated antigen defined by a monoclonal antibody produced from murine spleen cells immunized with human colorectal cancer cell lines 1, 2
• It exists in tissue as an epitope of sialylated Lewis A blood group antigen 1, 2
• A radioimmunometric assay is available for quantitation of CA 19-9 in blood 1
• Approximately 5-10% of the population is genotypically Lewis ab-negative and cannot produce CA 19-9, making testing ineffective in these individuals 1, 2, 3

Limitations of CA 19-9 as a Diagnostic Tool

• CA 19-9 is not specific for pancreatic cancer and can be elevated in:
  • Other gastrointestinal tumors (upper GI tract, ovarian, hepatocellular, colorectal) 1, 2
  • Inflammatory conditions of the hepatobiliary system 1, 4
  • Benign conditions such as thyroid disease 1
  • Biliary obstruction (both malignant and benign cases) 1, 5
• Small pancreatic tumors may not cause CA 19-9 elevation 1
• The sensitivity is approximately 80% and specificity about 90% for symptomatic patients 5, 4
• False positive results occur in 10-60% of patients with obstructive jaundice 3

Clinical Applications of CA 19-9

Not Recommended Uses:

• Screening: CA 19-9 is not recommended as a screening test for pancreatic cancer in asymptomatic individuals 1, 3
• Determining operability: CA 19-9 testing alone is not recommended for determining operability of pancreatic cancer 1
• Confirming recurrence: CA 19-9 determinations by themselves cannot provide definitive evidence of disease recurrence without confirmation by imaging studies and/or biopsy 1

Potential Clinical Uses:

• Monitoring treatment response: CA 19-9 can be measured at the start of treatment for locally advanced or metastatic disease and every 1-3 months during active treatment 1
  • Rising levels may indicate progressive disease, but confirmation with other studies is required 1
• Prognostic information:
  • Preoperative levels >1000 U/ml suggest unresectable disease in 96% of cases 5
  • Patients who normalize CA 19-9 postoperatively have longer survival than those who don't 5, 3
• Predicting recurrence: Serial measurements may predict disease recurrence before radiographic or clinical findings 5

Important Caveats

• Always confirm abnormal CA 19-9 results with imaging studies and/or biopsy 1
• Determine Lewis antigen status when interpreting CA 19-9 results, as 5-10% of the population cannot produce this antigen 2, 3
• Consider that acute cholangitis and cirrhosis can significantly elevate CA 19-9 levels 5
• Normal baseline CA 19-9 levels are associated with better long-term survival 4
• A decrease in CA 19-9 levels by ≥20-50% from baseline following treatment is associated with prolonged survival 3

Current Status

• Despite its limitations, CA 19-9 remains the only validated serum biomarker for pancreatic cancer in widespread clinical use 6, 3
• Numerous other potential biomarkers have been proposed but lack large-scale validation 6