Challenges in evaluation of screening for gastric cancer among men based on nonrandomized design

Abstract

Background: Objective was to quantify biases in screening for gastric cancer when comparing attenders to nonattenders using serum pepsinogen I (SPGI) level as primary test. Methods: In mid 1990s, all men aged 51–65 years from two Finnish cities were invited to SPGI screening. Mortality and premature mortality in attenders were compared to nonattenders. Efficacy of screening was studied by 15 years’ follow-up of standardized mortality ratio (SMR) and potential years of life lost (PYLL) due to gastric cancer. Bias due to selective attendance was quantified using corrective coefficients based on total cancer incidence and mortality, and gastric cancer-specific incidence and mortality for total population and nonattenders. Results: In 1994–1996, men aged 51–65 years (16,872) were invited to SPGI assay and 12,175 men (72%) attended. SPGI was 25 microg/l or less in 610 (5%) men, indicating severe atrophic gastritis (AG). Post-screening gastroscopy was performed to 435 men with low SPGI. Of these, 168 men were referred for treatment due to abnormal focal lesions. Attributable proportions in reductions of SMR and PYLL from gastric cancer due to screening were 59% and 67%. After correcting for selective participation, attributable proportions were reduced to 23% and 39%. Conclusions: Biomarker screening by low SPGI among middle-aged men followed by upper gastrointestinal endoscopy decreased long-term and premature mortality due to gastric cancer. However, in spite of methodological corrections done, the results do not justify any firm conclusions or recommend general screening programs. Randomized trials are warranted for this purpose.