CA 19-9

What it isA carbohydrate antigen shed by pancreatic, biliary, and some gastrointestinal cancers.

DoesMonitors pancreatic and biliary cancer treatment response and recurrence; not for screening.

GoodA low CA 19-9 in a patient with treated pancreatic cancer signals disease control.

BadElevated CA 19-9 can indicate pancreatic or biliary malignancy but also rises in benign biliary obstruction, pancreatitis, and cirrhosis. Some people lack the enzyme to produce it and run falsely low.