Retrospective Evaluation of Treatment Response in Patients with Nonmetastatic Pancreatic Cancer Using CT and CA 19-9

Background: Imaging studies have limitations in evaluating pancreatic ductal adenocarcinoma (PDAC) treatment response. Purpose: To investigate the effectiveness of combined CT and carbohydrate antigen 19-9 (CA 19-9) evaluation at 8 weeks after first-line treatment to predict overall survival (OS) of patients with nonmetastatic PDAC. Materials and Methods: Patients with nonmetastatic PDAC who received first-line treatment with either chemotherapy or concurrent chemoradiation in a single-center PDAC cohort registry were retrospectively enrolled in the study between January 2013 and December 2016. Follow-up CT images obtained 8 weeks after treatment were evaluated according to Response Evaluation Criteria in Solid Tumors. Patients with partial response (PR) or stable disease (SD) were defined as CT responders, and those with progressive disease (PD) were defined as CT nonresponders. Patients with a normalized CA 19-9 level at 8-week follow-up were defined as CA 19-9 responders, and those with a nonnormalized or nonelevated CA 19-9 level were defined as CA 19-9 nonresponders. OS was compared using the Kaplan-Meier method with Breslow analysis. Results: A total of 197 patients (mean age +/- standard deviation, 65 years +/- 10; 107 men) were evaluated. Patients with PD (n = 17) showed shorter OS than those with SD (n = 147; P,.001) or PR (n = 33; P =.003). OS did not differ between the patients with PR and those with SD (P =.60). When the CT and CA 19-9 responses were integrated, OS was longest in CT and CA 19-9 responders (group 1, n = 27; median OS, 26.6 months [95% CI: 9.0, 44.1]), followed by CT responders but CA 19-9 nonresponders (group 2, n = 153; median OS, 15.9 months [95% CI: 13.3, 18.5]; P =.007 vs group 1) and CT and CA 19-9 nonresponders (group 3, n = 17; median OS, 6.5 months [95% CI: 0.8, 12.2]; P,.001 vs group 2). Conclusion: Integrated evaluation with CT and carbohydrate antigen 19-9 response allowed more accurate stratification of survival in patients with pancreatic ductal adenocarcinoma in the early treatment period than did evaluation according to Response Evaluation Criteria in Solid Tumors. (C) RSNA, 2022