The validation of candidate
biomarkers often is hampered by the lack of a reliable means of assessing and comparing performance. We present here a reference set of serum and plasma samples to facilitate the validation of
biomarkers for resectable
pancreatic cancer. The reference set includes a large cohort of stage I-II
pancreatic cancer patients, recruited from 5 different institutions, and relevant control groups. We characterized the performance of the current best serological
biomarker for
pancreatic cancer, CA 19-9, using plasma samples from the reference set to provide a benchmark for future
biomarker studies and to further our knowledge of CA 19-9 in early-stage
pancreatic cancer and the control groups. CA 19-9 distinguished
pancreatic cancers from the healthy and
chronic pancreatitis groups with an average sensitivity and specificity of 70-74%, similar to previous studies using all stages of
pancreatic cancer.
Chronic pancreatitis patients did not show CA 19-9 elevations, but patients with benign biliary obstruction had elevations nearly as high as the
cancer patients. We gained additional information about the
biomarker by comparing two distinct assays. The two CA 9-9 assays agreed well in overall performance but diverged in measurements of individual samples, potentially due to subtle differences in antibody specificity as revealed by
glycan array analysis. Thus, the reference set promises be a valuable resource for
biomarker validation and comparison, and the CA 19-9 data presented here will be useful for benchmarking and for exploring relationships to CA 19-9.