How long should we continue gastric cancer screening? From an epidemiological point of view

BACKGROUND: In Japan, incidence of gastric cancer is expected to follow the current downward trend as the younger generation has lower incidence of Helicobacter pylori infection. In this study we aimed to estimate how long gastric cancer screening is deemed necessary in the future from epidemiologic perspectives. METHODS: Following the Japanese guidelines for gastric cancer screening 2014, recommendation of providing population-based gastric cancer screening is judged by balancing benefits and harms. Benefits and harms are estimated by number needed to screen (NNS) < 1000 and Number Needed to Recall (NNR) < 100. NNS is the number of people required to participate in a screening to prevent one death and NNR is the number of people required to undergo diagnostic examination to prevent one death. These index are estimated for 2020–2035 using future projections of gastric cancer mortality for the scenarios of relative risk (RR) of 0.5–0.9 for mortality reduction by the screening. RESULTS: The criteria of both NNS < 1000 and NNR < 100 are fulfilled for the following age groups: when RR is set as 0.6, men ≥ 55 and women ≥ 65; when RR is set as 0.7 and 0.8, men ≥ 65 and women ≥ 75; when RR is set as 0.9, men ≥ 75 only. CONCLUSIONS: In case of RR of 0.5 and 0.6, the gastric cancer screening are recommended for men ≥ 55 and women ≥ 65 until 2035, while it is not recommended for men and women in the 45–54 even in 2010 and 2015.