Incidental detection of cancers during population-based endoscopic gastric cancer screening in Japan

BACKGROUND: Upper gastrointestinal endoscopy traverses the full upper aerodigestive tract, unlike radiography, potentially enabling incidental detection of non-gastric malignancies. However, its population-level incidental detection rate for non-gastric upper aerodigestive tract cancers has not been systematically quantified. The aim of this study was to compare endoscopic screening with radiography and quantify detection of non-gastric upper aerodigestive tract cancers in a population-based setting. METHODS: This population-based cohort study was conducted by linking the Okayama City municipal gastric cancer screening registry with the Kokuho Database (KDB) for fiscal years 2016-2021. Among 36,326 participants contributing 64,822 screening examinations (40,832 radiography; 23,990 endoscopy), diagnoses of oral cavity, pharyngeal, laryngeal, and esophageal cancer occurring within 2 months of screening were ascertained from the KDB. Generalized estimating equations with modified Poisson regression were used to estimate adjusted risk ratios (aRRs) comparing endoscopy with radiography. RESULTS: Endoscopic screening was significantly associated with higher composite incidental detection rates for non-gastric upper aerodigestive tract cancers (95.9 vs. 34.3 per 100,000 examinations; aRR 2.94, 95% confidence interval [CI] 1.50-5.76; p = 0.002). Specifically, esophageal cancer detection was markedly higher with endoscopy (83.4 vs. 17.1 per 100,000; aRR 5.16, 95% CI 2.16-12.32; p < 0.001). No statistically significant differences were observed for oral cavity, pharyngeal, or laryngeal cancers. CONCLUSIONS: Endoscopic gastric cancer screening is associated with substantially higher incidental detection of non-gastric upper aerodigestive tract cancers, particularly esophageal cancer. These findings suggest an additional detection value for endoscopy that extends beyond its primary gastric cancer target in organized screening programs.