Clinical Role of CA 19-9

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CA 19-9 serves as the primary tumor marker for pancreatic adenocarcinoma monitoring, though it lacks specificity for pancreatic cancer diagnosis. Approximately 80% of patients with pancreatic cancer exhibit elevated CA 19-9 levels, whereas patients with Lewis antigen–negative status cannot express this marker. Baseline CA 19-9 measurement is recommended as part of standard staging workup, along with upper endoscopy, biopsy, endoscopic retrograde cholangiopancreatography (ERCP), and biliary stent placement when indicated.

Several factors can falsely elevate CA 19-9 levels, including inflammation and biliary obstruction, making it unreliable for diagnosing advanced disease in the presence of these conditions. For accurate baseline measurement, biliary obstruction should be relieved and bilirubin normalized before obtaining CA 19-9 levels. In this case, the patient required ERCP with stent placement due to elevated bilirubin and biliary obstruction before accurate tumor marker assessment.

In patients with preserved liver function and relieved biliary obstruction, higher CA 19-9 levels generally correlate with increased disease volume and more aggressive tumor behavior. Although not diagnostic, CA 19-9 serves as a reasonable marker for disease monitoring during treatment and surveillance for recurrence in patients fortunate enough to undergo surgical resection. Serial CA 19-9 measurements can help assess treatment response and detect disease progression, though interpretation must consider clinical context and potential confounding factors.