Objective: Serum carbohydrate antigen 19-9 (CA19-9) has never been compared to radiographic objective response as a surrogate for clinical outcomes in patients receiving chemotherapy for metastatic pancreatic cancer.
Methods: We compared CA19-9 decline to objective response as surrogate end points for both time to progression (TTP) and overall survival (OS) in patients with metastatic pancreatic cancer receiving fixed-dose rate gemcitabine.
Results: A total of 75 patients from 2 studies were eligible for analysis. Significant correlations were observed between maximum CA19-9 decline and both TTP (P < 0.0001) and OS (P < 0.0001). Median OS was 12.2 months for patients with more than a 75% decline in CA19-9, 7.5 months for those with 0% to 75% decline, and 3.5 months for those with no decline. Correlations between best radiographic response and both TTP (P < 0.0001) and OS (P=0.0013) were also observed. Median OS was 12.8 months for patients with partial or complete response, 8.0 months for those with stable disease, and 4.6 months for those with progressive disease.
Conclusions: CA19-9 decline compares favorably with objective response as a strong predictor of TTP and OS. CA19-9 could represent amore cost-effective tool for the evaluation of new therapies and guidance of clinical management in patients with metastatic pancreatic cancer.