Gastric cancer after positive screening faecal occult blood testing and negative assessment

Abstract

Background Gastric cancer may be suspected with otherwise unexplained positive faecal occult blood testing. Aims To assess the frequency of gastric cancer following positive faecal occult blood testing and negative colonoscopy. Subjects Age 40–74 cohort at first screening (1985–2001) with (a) faecal occult blood testing− (83,489), (b) faecal occult blood testing +/colonoscopy+ (2025), or faecal occult blood testing+/colonoscopy− (3555). Methods Gastric cancer incidence in faecal occult blood testing subsets, compared with expected standardized incidence rates. Results Gastric cancer risk was increased (standardized incidence rate = 146.7; 95% confidence interval: 105.8–203.4) in faecal occult blood testing+/colonoscopy− subjects. A four-fold excess incidence occurred during first year (observed cases = 10, standardized incidence rate = 408.3; 95% confidence interval: 219.7–758.8), irrespective of faecal occult blood testing type (guaiac, immunological). No excess risk occurred in faecal occult blood testing− (observed cases = 53, standardized incidence rate = 91.2; 95% confidence interval: 84.1–98.8) or in faecal occult blood testing+/colonoscopy+ subjects (observed cases = 2, standardized incidence rate = 101.9; 95% confidence interval: 25.5–407.4). Assuming a 100% 3-year study sensitivity for gastric cancer, faecal occult blood testing positive predictive value would be 0.4% (40–74 years) or 0.7% (≥60 years) in faecal occult blood testing+/colonoscopy− subjects. Conclusions Data suggest an association of faecal occult blood testing+/colonoscopy− and excess gastric cancer incidence in the following year. Due to low faecal occult blood testing+ positive predictive value, routine upper digestive tract endoscopy in these subjects is questionable.