Incremental diagnostic yield and tracer discordance of [18 F]FDOPA relative to [68Ga]Ga-DOTA-peptide PET in well-differentiated intestinal neuroendocrine tumors: a systematic review.

Somatostatin receptor positron emission tomography (SSTR PET) characterizes receptor expression and supports peptide receptor radionuclide therapy (PRRT) eligibility, whereas [18 F]fluorodihydroxyphenylalanine ([18 F]FDOPA) reflects amine-precursor handling. We systematically reviewed incremental diagnostic yield-defined as additional imaging-detected disease rather than demonstrated clinical benefit-and directional discordance between paired [18 F]FDOPA and [68Ga]Ga-DOTA-peptide PET in well-differentiated intestinal neuroendocrine tumors. PubMed, Scopus, and Web of Science were searched to 26 July 2026. Seven reports representing six diagnostic cohorts and one probable overlapping PRRT companion report were included. Compatible patient-level 2 × 2 tables were reconstructable in four reports; one historical two-patient subgroup was fully concordant. In the three informative cohorts (80 patients), only eight patients were discordant (three [18 F]FDOPA-only and five DOTA-peptide-only), with different directions across clinically heterogeneous studies; no pooled matched effect was estimated. At lesion level, [18 F]FDOPA often depicted additional hepatic, peritoneal, nodal, and pulmonary sites, but counts were clustered within patients. Serotonin/5-hydroxyindoleacetic acid associations were exploratory and did not define a selection threshold. No study established management or survival benefit. PRRT evidence was limited to eight patients. Current evidence supports task-specific interpretation of complementary imaging phenotypes, not routine dual-tracer imaging. [18 F]FDOPA cannot replace validated SSTR PET for receptor characterization or PRRT eligibility.