From the Guidelines
Carbohydrate Antigen 19-9 (CA 19-9) is a tumor marker primarily used to monitor pancreatic cancer treatment and detect recurrence after treatment, with the most recent and highest quality evidence suggesting its value in prognosticating disease burden and guiding treatment decisions 1.
Definition and Use
CA 19-9 is a type of glycoprotein found on the surface of certain cancer cells and released into the bloodstream. While CA 19-9 is most commonly associated with pancreatic cancer, elevated levels can also be found in other gastrointestinal cancers such as bile duct cancer, colorectal cancer, and stomach cancer.
Limitations
Normal CA 19-9 levels are typically below 37 U/mL, though this can vary between laboratories. It's essential to understand that CA 19-9 is not recommended as a screening test for the general population because it lacks sufficient sensitivity and specificity, as noted in studies such as 1. False positives can occur in benign conditions like pancreatitis, liver cirrhosis, and cholangitis. Additionally, about 5-10% of the population cannot produce CA 19-9 due to genetic factors, which can lead to false negatives, as discussed in 1 and 1.
Clinical Utility
CA 19-9 is most valuable when used to monitor treatment response in patients with known pancreatic cancer, where decreasing levels often indicate effective treatment while rising levels may suggest disease progression, as supported by evidence from 1 and 1. The use of CA 19-9 in monitoring and its prognostic value is further emphasized by its inclusion in guidelines for the management of pancreatic cancer, such as those discussed in 1.
Key Points
- CA 19-9 is primarily used for monitoring pancreatic cancer treatment and detecting recurrence.
- It lacks sufficient sensitivity and specificity for screening the general population.
- False positives and negatives can occur due to various factors, including benign conditions and genetic variations.
- CA 19-9 is valuable in monitoring treatment response and prognosticating disease burden in known pancreatic cancer cases.
From the Research
Definition of CA 19-9
- CA 19-9, also known as carbohydrate antigen 19-9 or cancer antigen 19-9, is a serum tumor marker used primarily for the diagnosis and monitoring of pancreatic cancer 2, 3, 4.
- It is a sialylated Lewis a antigen that is normally synthesized by normal human pancreatic and biliary ductal cells, as well as by gastric, colon, endometrial, and salivary epithelia 2.
Clinical Use of CA 19-9
- CA 19-9 is the most commonly used and best-validated serum tumor marker for pancreatic cancer diagnosis in symptomatic patients and for monitoring therapy in patients with pancreatic adenocarcinoma 2.
- The serum level of CA 19-9 can provide important information regarding prognosis, overall survival, and response to chemotherapy, as well as predict post-operative recurrence 3, 4.
- However, CA 19-9 has several limitations, including poor sensitivity, false negative results in subjects with Lewis (a-b-) genotype, and false positive elevation in patients with benign diseases 2, 3, 4.
Interpretation of CA 19-9 Levels
- Elevated CA 19-9 levels can be found in patients with benign as well as malignant diseases, including pancreatic, gastric, and hepatobiliary malignancies, and benign conditions such as disease of the hepatobiliary system, pneumonia, pleural effusion, renal failure, and SLE 5.
- CA 19-9 levels should be interpreted in the light of the clinical presentation of the patient, and awareness of the benign conditions that can be associated with increased levels of this marker is essential 5.
- Normalization of CA 19-9 levels following neoadjuvant therapy is a strong prognostic marker for long-term survival in patients with localized pancreatic cancer 6.
Prognostic Value of CA 19-9
- Pre-operative CA 19-9 serum levels can provide useful prognostic information, with patients having normal levels (<37 U/mL) having a prolonged median survival compared to those with elevated levels (>37 U/mL) 3, 4.
- A CA 19-9 serum level of <100 U/mL implies likely resectable disease, whereas levels >100 U/mL may suggest unresectability or metastatic disease 3, 4.
- Failure to normalize pre-operative or post-operative CA 19-9 levels is associated with an increased risk of death in patients with pancreatic cancer 6.