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BACKGROUND & AIMS: The prognostic role of plasma chromogranin A in patients with neuroendocrine tumors is unclear. We investigated the role of chromogranin A in predicting survival and hypothesized that chromogranin A mirrors tumor burden and that a rapid increase after a phase of stable plasma chromogranin A levels might predict exploding tumor growth. METHODS: Three hundred forty-four patients with metastatic, well-differentiated neuroendocrine tumors were included. A subsample of 102 patients was investigated to correlate radiologically classified tumor burden with plasma chromogranin A. Hepatic tumor burden (0%, 0%-25%, 25%-50%, >50%) was assessed from computed tomography/magnetic resonance imaging scans. Follow-up information until death was generated in regular intervals. RESULTS: Plasma chromogranin A levels (U/L) vary between tumor entities (Kruskal-Wallis, P < .001) and were associated with survival time (hazard ratio [hours], 2.14 per one unit in the log(10) CgA level scale; 95% confidence interval [CI], 1.75-2.62; P < .001). Chromogranin A levels correlated with hepatic tumor burden (Spearman P = .57; 95% CI, 0.44-0.70; P < .001). Additional extrahepatic tumor load did not relevantly affect plasma chromogranin A. A sudden increase observed in individual patients was paralleled by rapid tumor progress and short survival. CONCLUSIONS: Increased plasma chromogranin A in patients with metastatic neuroendocrine tumors is predictive for shorter survival. There was a modest correlation between chromogranin A levels and hepatic tumor burden. We hypothesized further that a sudden increase in individual chromogranin A levels indicates unfavorable outcome.