What is the use of checking Carbohydrate Antigen 19-9 (CA 19-9) levels?

From the Guidelines

The primary use of checking Carbohydrate Antigen 19-9 (CA 19-9) levels is to monitor pancreatic cancer and assess treatment effectiveness, rather than as a screening tool for the general population. CA 19-9 is a tumor marker that can be elevated in other gastrointestinal cancers, including biliary tract, colorectal, and gastric cancers. Normal CA 19-9 levels are typically below 37 U/mL, though this can vary by laboratory 1. It's essential to understand that CA 19-9 has limitations, such as approximately 5-10% of the population being unable to produce this marker due to genetic factors, and levels can also rise in non-cancerous conditions like pancreatitis, cirrhosis, and cholangitis 1.

Some key points to consider when using CA 19-9 include:

• CA 19-9 is the most useful tumor marker in pancreatic cancer 1
• Staging of pancreatic cancer is initially done by CT scan, with EUS providing complementary information and allowing biopsy of the tumor 1
• MRI should be discussed, especially in cystic lesions 1
• CA 19-9 can be measured every 1 to 3 months for patients with locally advanced or metastatic disease receiving active therapy 1
• Elevations in serial CA 19-9 determinations suggest progressive disease, but confirmation with other studies should be sought 1

For optimal clinical use, CA 19-9 should be interpreted alongside other diagnostic tests, such as imaging studies and biopsies, and serial measurements over time are more informative than single readings 1. Physicians typically order this test when monitoring known pancreatic cancer, evaluating treatment response, or investigating symptoms suggestive of pancreatic pathology 1. In summary, CA 19-9 is a valuable tool in the management of pancreatic cancer, but its use should be guided by a thorough understanding of its limitations and in conjunction with other diagnostic modalities.

From the Research

Uses of Checking CA 19-9 Levels

• CA 19-9 is a tumor marker used primarily in the diagnosis and management of pancreatic cancer 2, 3.
• It can aid in the diagnosis of pancreatic cancer, particularly in symptomatic patients, with a sensitivity and specificity of 79-81% and 82-90%, respectively 3.
• CA 19-9 levels can provide prognostic information, with higher levels associated with advanced tumor stage, unresectable disease, and poorer survival outcomes 2, 3, 4.
• The marker can be used to monitor response to treatment, including surgery and chemotherapy, with decreasing levels indicating a favorable response 3, 5, 6.
• CA 19-9 can also be used for postoperative follow-up, with elevated levels potentially indicating recurrence, often before it can be detected by imaging studies like ultrasound 6.

Limitations of CA 19-9

• CA 19-9 has limited sensitivity and specificity due to false negatives in patients with the Lewis negative phenotype and false positives in the presence of obstructive jaundice 3.
• It is not suitable for screening asymptomatic populations due to its low sensitivity and specificity in this context 3.
• CA 19-9 levels can be elevated in other conditions, including benign diseases and other types of cancer, which can limit its utility as a specific marker for pancreatic cancer 2, 3.

Clinical Applications

• Preoperative CA 19-9 levels can help predict resectability and prognosis in patients with pancreatic cancer 2, 3.
• Postoperative monitoring of CA 19-9 levels can help detect early recurrence and guide further management 5, 6.
• CA 19-9 levels can be used in conjunction with other diagnostic tools and clinical assessments to improve the management of pancreatic cancer patients 2, 3, 4.