The sTRA Plasma Biomarker: Blinded Validation of Improved Accuracy over CA19-9 in Pancreatic Cancer Diagnosis

Purpose: The CA19-9 biomarker is elevated in a substantial group of patients with pancreatic ductal adenocarcinoma (PDAC), but not enough to be reliable for the detection or diagnosis of the disease. We hypothesized that a glycan called sTRA is a biomarker for PDAC that improves upon CA19-9. Experimental Design: We examined sTRA and CA19-9 expression and secretion in panels of cell lines, patient-derived xenografts, and primary tumors. We developed candidate biomarkers from sTRA and CA19-9 in a training set of 147 plasma samples and used the panels to make case/control calls, based on predetermined thresholds, in a 50-sample validation set and a blinded, 147-sample test set. Results: The sTRA glycan was produced and secreted by pancreatic tumors and models that did not produce and secrete CA19-9. Two biomarker panels improved upon CA19-9 in the training set, one optimized for specificity, which included CA19-9 and two versions of the sTRA assay, and another optimized for sensitivity, which included two sTRA assays. Both panels achieved statistical improvement (p < 0.001) over CA19-9 in the validation set, and the specificity-optimized panel achieved statistical improvement (p < 0.001) in the blinded set: 95% specificity and 54% sensitivity (75% accuracy), compared to 97%/30% (65% accuracy). Unblinding produced further improvements and revealed independent, complementary contributions from each marker. Conclusions: sTRA is a validated serological biomarker of PDAC that yields improved performance over CA19-9. The new panels may enable surveillance for PDAC among people with elevated risk, or improved differential diagnosis among patients with suspected pancreatic cancer.

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