Combination of CA19-9 and Blood Free-Circulating Methylated RUNX3 May Be Useful to Diagnose Stage I Pancreatic Cancer

Background: Although serum carbohydrate antigen 19-9 (CA19-9) is widely used as a useful biomarker of pancreatic cancer for monitoring the response to therapy, it is not recommended for screening of early pancreatic cancer because of its limited sensitivity for small tumors. Thus, it is critical to discover novel serum biomarkers to complement CA19-9 in order to improve sensitivity. Although methylated runt-related transcription factor 3 (RUNX3) is a biomarker of pancreatic cancer, its detection by conventional bisulfite-based methylation assays from a small serum sample amount is very difficult. Therefore, we developed a new methylation assay, the combined restriction digital PCR (CORD) assay, that enables counting of even one copy of a methylated gene in a small DNA sample amount without DNA bisulfite treatment. Objectives: We evaluated the sensitivity and specificity of serum DNA testing of methylated RUNX3 by the CORD assay in combination with and without CA19-9 for the detection of pancreatic cancer in 55 patients with pancreatic cancer, 12 patients with benign pancreatic disease, and 80 healthy individuals. Results: The CORD assay of methylated RUNX3 had a sensitivity of 50.9% (28/55) and specificity of 93.5% (86/92). Combination of the CORD assay of methylated RUNX3 and CA19-9 resulted in a sensitivity of 85.5% (47/55) and specificity of 93.5% (86/92) for all stages of pancreatic cancer and a sensitivity of 77.8% (7/9) for stage I pancreatic cancer. Conclusions: ombination of the CORD assay and CA19-9 may provide an alternative screening strategy for detecting early-stage pancreatic cancer.