What Happens to Serum Carbohydrate Antigen 19-9 after Biliary Stent Placement in Pancreaticobiliary Malignancy?

Abstract

Purpose: CA19-9 is frequently followed to monitor disease progression. Bile duct obstruction has been associated with increased CA19-9. The purpose was to evaluate the correlation of CA 19–9 with the regression of bilirubin after stent placement for malignant biliary obstruction. The hypothesis was that biliary decompression would result in a downward trend of CA19-9. Methods: The records at MD Anderson Cancer Center were reviewed for patients who underwent first time ERCP with biliary stent placement for malignant obstructive jaundice from Oct. 2002 to Sept. 2005. Patients who achieved serum bilirubin ≤ 2 mg/dL and those with adequate CA19-9 data were identified and analyzed to determine association. CA19-9 levels needed to have been recorded within 15 days prior to stent placement and then post stent when bilirubin ≤ 2. Other examined variables included type of cancer, presence of metastasis, and level of pre-stent bilirubin. Statistics: Spearman rank correlation methods were used to assess the correlation between variables. Fisher's exact test was performed. Results: A total of 52 patients with adequate serum CA 19–9 data who achieved bilirubin ≤ 2 after biliary stent placement were identified (pre-stent bilirubin range 2.8–21.9 mg/dL; mean 10.23; median 9.4). Forty (77%) had pancreatic cancer, 12 (23%) other biliary malignancies, and 23 (44%) with liver metastasis. 27/52 (52%) demonstrated a downward trend of CA19-9 post stent, 16/52 (31%) an upward trend, and 9/52 (17%) an equivocal change (defined arbitrarily as a change less than 20 U/mL). Although a change of CA19-9 was significantly correlated with bilirubin regression (Spearman correlation coefficient 0.36 and p= 0.009), the direction of change in CA 19–9 was variable. Patients whose CA19-9 decreased had significantly higher baseline bilirubin as compared with patients whose CA19-9 level increased (p= 0.02). The change of CA19-9 was not significantly associated with cancer diagnosis (pancreatic vs other) (p= 0.16) or the presence of liver metastasis (p= 0.22). Conclusions: Unlike the regression of CA 19–9 post stent placement in benign biliary obstruction, the change in CA 19–9 is unpredictable in cases of malignant biliary obstruction despite adequate biliary decompression and bilirubin regression. Further studies are necessary to find other confounding variables affecting CA 19–9 i.e. tumor burden.