What is the utility of CA19-9 (Cancer Antigen 19-9) in diagnosing pancreatic cancer when a pancreatic mass is seen on a computed tomography (CT) scan?

From the Guidelines

CA19-9 is not useful for the primary diagnosis of pancreatic cancer, but it has significant value as a prognostic factor and can be used to measure disease burden and guide treatment decisions. When a pancreatic mass is seen on a CT scan, CA19-9 can be elevated in almost 80% of patients with advanced disease 1. However, its levels can be falsely elevated in benign conditions like pancreatitis, cholangitis, and cirrhosis, and approximately 7-10% of the population cannot produce this marker due to genetic factors (Lea-b- genotype) 1.

Key Points to Consider

• The normal range of CA19-9 is typically below 37 U/mL, but this can vary depending on the laboratory and assay used.
• CA19-9 levels should be interpreted cautiously, considering the clinical presentation and imaging findings.
• Very high levels of CA19-9 (>500 U/mL) can indicate a worse prognosis after surgery 1.
• CA19-9 is particularly useful for monitoring treatment response and recurrence after initial therapy.
• Definitive diagnosis of pancreatic cancer still requires tissue sampling through fine needle aspiration or biopsy, as recommended by the American Society of Clinical Oncology 1.

Diagnostic Approach

• A multiphase computed tomography scan of the abdomen and pelvis using a pancreatic protocol or magnetic resonance imaging should be performed to assess the anatomic relationships of the primary tumor and to assess for the presence of intra-abdominal metastases 1.
• Endoscopic ultrasonography and/or diagnostic laparoscopy may be used as supplemental studies to facilitate acquisition of a biopsy specimen 1.
• A serum level of CA 19-9 and baseline standard laboratory studies should be assayed to evaluate the patient's condition and guide treatment decisions 1.

From the Research

Utility of CA19-9 in Diagnosing Pancreatic Cancer

• CA19-9 is a tumor-associated antigen that can be elevated in pancreatic cancer, but its utility as a diagnostic marker is limited by its lack of specificity and sensitivity 2, 3, 4.
• A study published in 1994 found that CA19-9 > 90 U/ml is highly suggestive of pancreatic malignancy, while CA19-9 > 200 U/ml is virtually diagnostic of pancreatic malignancy 2.
• However, another study published in 2011 noted that CA19-9 has a sensitivity and specificity of 79-81% and 82-90%, respectively, for the diagnosis of pancreatic cancer in symptomatic patients 3.
• CA19-9 can be elevated in benign conditions, such as obstructive jaundice, and can be falsely negative in patients with a Lewis negative phenotype 3, 4.
• A study published in 2003 found that elevated CA19-9 levels can be found in patients with benign as well as malignant disease, and that CA19-9 levels should be interpreted in the context of the patient's clinical presentation 4.
• CA19-9 can be used to provide prognostic information, with higher levels associated with more advanced disease and poorer outcomes 3, 5.
• Normalization of CA19-9 levels after neoadjuvant therapy is associated with improved survival in patients with localized pancreatic cancer 5.

Limitations of CA19-9

• CA19-9 is not suitable for screening asymptomatic populations for pancreatic cancer due to its low sensitivity and specificity 3, 6.
• CA19-9 can be elevated in other malignancies, such as colorectal, lung, and ovarian cancer, which can limit its utility as a diagnostic marker for pancreatic cancer 4.
• False-positive elevations of CA19-9 can occur in benign conditions, such as hepatobiliary disease, pneumonia, and renal failure 4.