Why Doctors Order the CA 19-9 Tumor Marker Test to Confirm or Rule Out Pancreatic Cancer
written by: niknak
• edited by: Emma Lloyd
• updated: 6/4/2011
There have been significant advances in the understanding of pancreatic cancer at the molecular level and in the treatment of early-stage tumors. A blood test for pancreatic cancer is possible by measurement of serum CA 19-9, which can be a useful biomarker for the disease.
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Pancreatic Cancer Facts
Pancreatic cancer is the fourth highest cause of cancer-related death inthe USA. Less than 20% of patients present with disease that is curable and the average 5-year survival rate is below 5%.
Environmental risk factors for pancreatic cancer include smoking and high fat diets. Some studies show an increased incidence of pancreaticcancer among patients with a history of diabetes, chronicpancreatitis or chronic cirrhosis.
Pancreatic cancer results from the accumulation of successive genetic mutations. Pre-malignant lesions develop in the ductal epithelium and develop into invasive disease.
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Clinical Signs and Symptoms of Pancreatic Cancer
Symptoms of pancreatic cancer depend on the locationof the tumor within the gland and the stage of thedisease, but generally include:
abdominaldiscomfort and nausea.
pancreatitis (inflammation of the pancreas)
abnormal blood glucose levels
anorexia and weight loss.
hepatomegaly and ascites.
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Diagnostic Procedures for Pancreatic Cancer
Routine blood tests: may detect mild abnormalities in liver-function, hyperglycemia, anemia and increased insulin levels.
Computed tomography (CT): this allows visualizationof the primary tumor.
Endoscopicultrasonography: can be useful in patients where a pancreatic tumoris suspected but there is no visible massfrom CT. It allows tissue to be obtained for microscopic analysis.
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A Blood Test for Pancreatic Cancer: CA 19-9
There are numerous potential serum biomarkers for diagnosis of pancreatic cancer but so far, the tumor-associated antigen CA 19-9 is theonly one considered clinically useful.
CA 19-9 is a serum carbohydrate antigen. Serum levels rise in pancreatic cancer patients due to increased secretion of the antigen from malignant cells.
CA 19-9 isused for therapeutic monitoring and for early detection of recurrentdisease after treatment.Elevated levels of CA 19-9 correlate with tumour differentiation and the extent of disease. Preoperative CA 19-9 levels below 200 U/ml and normalisation after treatment has been associated with a longer disease-free survival. Elevation of serum CA 19-9 levels can be a good predictor of tumour recurrence.
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Limitations of the CA 19-9 Blood Test for Pancreatic Cancer
CA 19-9 is a sialyted Lewis blood group antigen. People who lack the Lewis antigen glycosyltransferase are unable to synthesise CA 19-9 (around 10% of the population). In this group of patients the level of CA 19-9 can be normal, even in advanced disease.
CA 19-9 may be elevated in other conditions such as cholestasis.
The sensitivity of the CA 19-9 test is variable. Up to 30% of pancreatic cancer patients do not have elevated CA 19-9.
Raised CA 19-9 can occur in benign inflammatory diseases of the pancreatobiliary tract.
Due to lower levels of CA 19-9 in localised pancreatic cancer, it is not useful as a marker of early disease.
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Pancreatic Cancer. M.Hidalgo. New England Journal of Medicine, April 2010,Vol 362 P1605-1617
Molecular Markers of Pancreatic Cancer: Development and Clinical Relevance. L.Fry, K.Mönkemüller&P.Malfertheiner, Langenbeck's Archives of Surgery, 2008, Vol 393, P883-90