Carbohydrate antigen 19-9 as a prognostic biomarker in pancreatic neuroendocrine tumors.

Carbohydrate antigen 19-9 (CA19-9) is not generally considered to be a biomarker in pancreatic neuroendocrine tumors (pNETs), as the majority of pNETs present with a normal range of CA19-9. The present study aimed to evaluate the role of serum CA19-9 levels as a prognostic factor in a relatively large number of patients with pNETs. Consecutive patients were retrospectively collected from a single institution between June 2006 and February 2015. The receiver operating characteristic (ROC) curve and the area under the ROC curve were used to select the cut-off values for the baseline CA19-9 levels. The primary end point was set as overall survival. Potential factors associated with the abnormal elevation of CA19-9 expression levels in pNETs were also investigated. The cut-off value for CA19-9 was 16 U/ml as determined by the ROC curve, and for the area under the ROC curve it was 0.68. In total, 32.7% of patients (51/156) had CA19-9 expression levels higher than the cut-off value. Univariate analysis demonstrated that CA19-9 >16 U/ml was an adverse prognostic factor for patients' overall survival. The CA19-9 >16 U/ml group had a statistically higher proportion of tumor node metastasis (TNM) stage III or IV, as compared with the CA19-9 ≤16 U/ml group. To the best of our knowledge, the present study is the first to demonstrate that CA19-9 is a prognostic biomarker of pNETs, one that may reflect its aggressiveness and severity.