From the Guidelines
CA 19-9 is a tumor marker that should be used in conjunction with imaging studies and clinical findings to monitor treatment response and detect recurrence in patients with pancreatic cancer or other gastrointestinal cancers, as it is not specific to pancreatic cancer and can be elevated in other conditions. The normal range of CA 19-9 is typically below 37 U/mL, with higher levels potentially indicating pancreatic cancer, particularly when values exceed 100 U/mL 1. However, CA 19-9 is not specific to pancreatic cancer and can be elevated in other conditions including biliary tract cancers, colorectal cancer, gastric cancer, and non-malignant conditions like pancreatitis, cirrhosis, and cholangitis 1. Some key points to consider when using CA 19-9 include:
- About 5-10% of the population cannot produce CA 19-9 due to genetic factors, resulting in false negatives 1.
- When monitoring pancreatic cancer treatment, CA 19-9 levels are typically measured before treatment begins to establish a baseline, then regularly during and after treatment to assess response 1.
- Rising levels may indicate disease progression or recurrence, while decreasing levels often suggest treatment effectiveness 1.
- CA 19-9 should always be interpreted alongside clinical findings, imaging studies, and other diagnostic tests rather than in isolation 1. In patients with primary sclerosing cholangitis (PSC), CA 19-9 can be used as a circulating marker to detect malignancies, particularly cholangiocarcinoma, but its sensitivity and specificity vary depending on the cut-off value used 1. The combination of serum CA 19-9 and imaging studies, such as MRI/MRCP or US, can improve the sensitivity and specificity of detecting hepatobiliary malignancies in PSC patients 1.
From the Research
CA 19-9 as a Biomarker for Pancreatic Cancer
- CA 19-9 is the most extensively studied and clinically useful biomarker for pancreatic cancer 2, 3
- It has a sensitivity and specificity of 79-81% and 82-90% respectively for the diagnosis of pancreatic cancer in symptomatic patients 2, 3
- CA 19-9 serum levels can provide important information with regards to prognosis, overall survival, and response to chemotherapy as well as predict post-operative recurrence 2, 3
Limitations of CA 19-9
- Poor sensitivity, false negative results in Lewis negative phenotype (5-10%), and increased false positivity in the presence of obstructive jaundice (10-60%) limit the universal applicability of serum CA 19-9 levels in pancreatic cancer management 2, 3
- Non-specific expression in several benign and malignant diseases also limits its use 2, 3
CA 19-9 in Treatment and Prognosis
- Pre-operative CA 19-9 serum levels provide useful prognostic information, with patients having normal levels (<37 U/mL) experiencing longer median survival compared to those with elevated levels (>37 U/mL) 2, 3
- A CA 19-9 serum level of <100 U/mL implies likely resectable disease, while levels >100 U/mL suggest unresectability or metastatic disease 2, 3
- 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 2, 3
- Elevated CA 19-9 level at treatment initiation demonstrates a prognostic impact, and routine serial monitoring of CA 19-9 levels during treatment may be warranted 4, 5