From the Guidelines
CA 19-9 is the most useful tumor marker in pancreatic cancer and should be used to monitor treatment response and detect recurrence in patients with known pancreatic cancer who had elevated levels at diagnosis 1.
Key Points
- CA 19-9 is not useful for the primary diagnosis of pancreatic cancer, as it has limited sensitivity and specificity 1.
- The marker may also be elevated in non-cancerous conditions such as pancreatitis, cholangitis, cirrhosis, and other inflammatory conditions of the digestive system, which can lead to false positive results 1.
- About 5-10% of the population cannot produce CA 19-9 due to genetic factors, resulting in false negatives even with active disease 1.
- For optimal clinical use, CA 19-9 should be interpreted alongside imaging studies, such as CT or MRI, and clinical findings rather than in isolation 1.
Clinical Use
- CA 19-9 levels can be used to monitor treatment response and detect recurrence in patients with known pancreatic cancer 1.
- A preoperative serum CA 19-9 level ≥500 UI/ml clearly indicates a worse prognosis after surgery 1.
- CA 19-9 can also be used to support a diagnosis of cholangiocarcinoma, although it is not specific for this condition 1.
Limitations
- CA 19-9 has limited sensitivity and specificity, and should not be used as a screening test for the general population 1.
- The marker can be elevated in non-cancerous conditions, leading to false positive results 1.
- Genetic factors can result in false negatives, even with active disease 1.
From the Research
CA 19-9 as a Biomarker
- CA 19-9 is the best validated biomarker for pancreatic cancer, with a sensitivity of approximately 80% 2
- It can be used as a biomarker, predictor, and promoter in pancreatic cancer 2
- The major challenges in using CA 19-9 as a biomarker include false positives in conditions of inflammation and non-pancreatic cancers, and false negatives in Lewis-negative individuals 2, 3, 4
Diagnosis and Prognosis
- CA 19-9 has a sensitivity and specificity of 79-81% and 82-90% respectively for the diagnosis of pancreatic cancer in symptomatic patients 3, 4
- Pre-operative CA 19-9 serum levels can provide useful prognostic information, with normal levels associated with prolonged median survival 3, 4
- A CA 19-9 serum level of <100 U/mL implies likely resectable disease, whereas levels >100 U/mL suggest unresectability or metastatic disease 3, 4
Monitoring and Management
- CA 19-9 levels can be used to monitor the response to neoadjuvant therapy and predict post-operative recurrence 5
- Normalization or a decrease in post-operative CA 19-9 serum levels by ≥20-50% from baseline following surgical resection or chemotherapy is associated with prolonged survival 3, 4
- CA 19-9 is an attractive therapeutic target for cancer, with strategies including therapeutic antibodies and vaccines, CA19-9-guided nanoparticles, and inhibition of CA19-9 biosynthesis 2
Limitations
- CA 19-9 has limitations, including poor sensitivity, false negative results in Lewis-negative phenotype, and increased false positivity in the presence of obstructive jaundice 3, 4
- Non-specific expression in several benign and malignant diseases also limits the universal applicability of serum CA 19-9 levels in pancreatic cancer management 3, 4