BACKGROUND AND AIM The role of carbohydrate antigen 19-9 (CA 19-9) for predicting treatment outcome in pancreatic ductal adenocarcinoma (PDAC) remains to be elucidated. This study was aimed to determine the correlation between early decrement in CA 19-9 concentration and prognosis of advanced PDAC after chemotherapy.

METHODS All patients confirmed with locally advanced or metastatic PDAC who received initial systemic chemotherapy for at least two cycles in our institution between January 2012 and December 2013 were included. Serum CA 19-9 concentrations at baseline and 8 weeks after the initiation of chemotherapy were obtained. Correlation between CA 19-9 decrement and survival outcomes (time to progression [TTP] and overall survival [OS]) were evaluated.

RESULTS A total of 183 patients with initially elevated CA 19-9 were included. OS and TTP was significantly longer for patients whose serum CA 19-9 concentration decreased more than 10% from baseline (n = 103), than that for patients whose serum CA 19-9 was not decreased (n = 80) (423 vs 155 days, P < 0.001 for OS and 222 vs 75 days, P < 0.001 for TTP). In multivariate analysis, CA 19-9 decrement more than 10% from baseline was still a significant factor for longer OS (hazard ratio for progression 0.275 [0.184-0.412], P < 0.001) and TTP (0.322 [0.219-0.473], P < 0.001) in both stage III and IV.

CONCLUSIONS The early decrement of CA 19-9 after the initiation of chemotherapy was an independent factor related with better survival outcomes in unresectable PDAC.