A new strategy for the application of CA19-9 in the differentiation of pancreaticobiliary cancer: analysis using a receiver operating characteristic curve

Abstract

OBJECTIVE: Clinicians might be misled in interpreting an elevated CA19-9 when differentiating pancreaticobiliary cancer from benign clinical conditions such as acute cholangitis or cholestasis, because in these conditions, the concentration of CA19-9 may also be elevated. The aims of our study were to calculate new individual cutoff values for CA19-9 according to clinical situations using a receiver operating characteristic (ROC) curve and to define a new strategy for interpreting CA19-9 in pancreaticobiliary cancer. METHODS: One hundred sixty patients with pancreatic diseases (cancer 90, benign disease 70), 322 patients with biliary tract diseases (biliary cancer 152, benign disease 170), and 20,035 asymptomatic controls were enrolled in the present study. An ROC curve was described by plotting the sensitivity on the y-axis against 1-specificity on the x-axis for each of several cutoff values. RESULTS: The area under the ROC curve was significantly greater for pancreatic cancer than for biliary cancer ( p < 0.05). For patients with pancreatic cancer, CA19-9 proved to be useful. At a cutoff value of 37 U/ml, sensitivity and specificity were 76.7% and 87.1%, respectively. For patients with biliary cancer, CA19-9 was not helpful. However, when patients with biliary disease were divided into two groups according to the presence of cholangitis or cholestasis, CA19-9 proved to be more useful for the group without cholangitis or cholestasis than for the group with cholangitis or cholestasis ( p < 0.05). In the former group, the sensitivity and specificity of CA19-9 were 77.6% and 83%, respectively, at the cutoff value of 37 U/ml. For the latter group, the sensitivity and specificity of CA19-9 were 74% and 41.5% respectively, whereas the specificity reached 87% at 300 U/ml. CA19-9 in diagnosing pancreatic cancer was useful regardless of accompanying acute pancreatitis or cholestasis. The serum concentration of CA19-9 in asymptomatic individuals was 9.42 ± 9.95 U/ml. Only 1 of 157 patients with a concentration of CA19-9 above 37 U/ml was found to have gallbladder cancer. The positive and negative predictive values were 0.65% and 0.78%, respectively. CONCLUSIONS: The use of CA19-9 for the differentiation of pancreaticobiliary cancer should be applied individually, depending on the clinical situation.