Abstract
PURPOSE: Gastroenteropancreatic neuroendocrine tumors (GEP-NET) are relatively indolent but can be more aggressive. The current recommendations for using serum chromogranin A (CgA) for patients with GEP-NET are equivocal. This study was designed to validate an automated CgA immunofluorescence assay for monitoring disease progression in patients with GEP-NET. PATIENTS AND METHODS: A prospective, multicenter, blinded observational study was designed to validate an automated CgA immunofluorescence assay for monitoring disease progression in patients with GEP-NET. Tumor progression was evaluated with RECIST 1.1 by CT/MRI. An increase ≥50% above the prior CgA concentration to a value >100 ng/mL in the following CgA concentration was considered positive. RESULTS: A total of 153 patients with GEP-NET were enrolled. Using the prespecified cut-off of CgA change for tumor progression, specificity was 93.4% (95% confidence interval, 90.4%-95.5%; P < 0.001), sensitivity 34.4% (25.6%-44.3%), positive predictive value 57.9% (45.0-69.8), negative predictive value 84.3% (80.5-87.6), and AUC 0.73 (0.67-0.79). CONCLUSIONS: Changes in serial measurements of serum CgA had a favorable specificity and negative predictive value, making this test a useful adjunct to routine radiographic monitoring.