Serum carboxypeptidase A activity as a biomarker for early-stage pancreatic carcinoma.

BACKGROUND: The early stage of pancreatic carcinoma lacks typical clinical signs and symptoms, and is difficult to diagnose. We developed an assay for active form of serum carboxypeptidase A (F-CPA) and its zymogen precursor pro CPA, and evaluated them as a marker for early-stage pancreatic carcinoma. METHODS: Serum CPA from 406 patients including 169 with pancreatic carcinoma, 53 with acute pancreatitis, 23 with chronic pancreatitis, and 161 with non-pancreatic diseases were assayed by a method with N-acetyl-phenylalanyl-l-3-thiaphenylalanine as substrate and dl-benzylsuccinic acid as specific inhibitor of CPA. Activation of pro CPA was carried out using trypsin. RESULTS: An established assay system was performed fully automatically and possesses enough performance for routine clinical assay. This system requires 31 minutes for CPA detection. No significant differences were detected between the F-CPA activity of patients with pancreatic carcinoma and that of patients with non-pancreatic diseases (p=0.168). F-CPA was mainly increased in patients with pancreatitis. Since total-CPA (T-CPA, T-CPA=pro CPA+F-CPA) was increased both in patients with pancreatic carcinoma and those with acute pancreatitis (p<0.0001, each case), the F-CPA/T-CPA ratio was low only in the patients with pancreatic carcinoma. The rate of positivity of T-CPA in the early stage of pancreatic carcinoma in which tumor was less than 2 cm was 77%, and higher than those of CA19-9 (31%), CEA (8%), and elastase 1 (46%). CONCLUSION: It was suggested that assays of both T-CPA and F-CPA in serum might be useful for the surveillance of early-stage pancreatic carcinoma.