Tumor M2-pyruvate kinase, a new metabolic marker for pancreatic cancer

An isoenzyme of pyruvate kinase (Tu M2-PK) is overexpressed by tumor cells and can be measured in blood by a specific immunoenzymatic assay. Our objective was to investigate the diagnostic value of Tu M2-PK in comparison with that of CA 19-9 in pancreatic cancer. We studied 265 subjects: 60 with histologically confirmed pancreatic cancer, 43 with benign pancreatic diseases (acute and chronic pancreatitis), 5 with benign cystic neoplasms of the pancreas, 9 with neuroendocrine tumors, 77 with other abdominal malignancies, 47 with benign digestive diseases, and 24 healthy controls. Levels of plasma Tu M2-PK and serum CA 19-9 were determined by commercially available specific immunoassays. The diagnostic sensitivity and specificity of Tu M2-PK for pancreatic cancer were 85 and 41%, respectively, while those of CA 19-9 were 75 and 81%. The combination of the two tests significantly increased sensitivity (97%) but lowered specificity (38%). In discriminating between pancreatic cancer and acute or chronic pancreatitis, Tu M2-PK turned out to be less accurate than CA 19-9. In patients without pancreatic tumor, cholestasis appeared not to affect the values of Tu M2-PK, while CA 19-9 was found to be significantly higher. Tu M2-PK was also abnormally high in the majority of patients with other digestive malignancies or neuroendocrine tumors. The results demonstrate that Tu M2-PK has a satisfactory sensitivity but a poor specificity in the diagnosis of pancreatic cancer. Used together with CA 19-9, the sensitivity increases considerably.