Serum chromogranin A levels for the diagnosis and follow-up of well-differentiated non-functioning neuroendocrine tumors.

Circulating chromogranin A (CgA) level is a useful marker for diagnosis and treatment efficacy monitoring of neuroendocrine tumors (NETs). To evaluate the diagnostic value of serum CgA in well-differentiated non-functioning NETs and to investigate the correlation between changes in serum CgA levels and imaging responses in patients with locally advanced or metastatic disease, 60 healthy controls and 82 patients with NETs (28 with localized NETs and 54 with advanced NETs) treated between December 2010 and November 2014 were included. CgA levels were determined by ELISA. Receiver-operating characteristic (ROC) curve analysis was used to evaluate the diagnostic sensitivity and specificity of serum CgA. Correlation between CgA levels and tumor burden was analyzed. Serial CgA measurements and tumor responses (evaluated according to the RECIST 1.1 criteria) in 40 patients with locally advanced or metastatic disease were recorded. Using a cutoff value of 84 ng/mL, the sensitivity of serum CgA was 67 %, with a specificity of 78 %. Serum CgA levels of patients with different tumor burdens were significantly different. Progressions were observed in 38 out of 122 visits. Using a 28 % increase of serum CgA concentration as the best cutoff value, the sensitivity and specificity were 79 and 86 %, respectively, with positive and negative predictive values of 71 and 90 %, respectively, to determine disease progression. Serum CgA measurement had a modest sensitivity for the diagnosis of non-functioning NETs. However, increases of CgA levels combined with imaging might be helpful in detecting tumor progression in patients with NETs.