This article [1] is very impressive and shows that Korea has an effective gastric cancer screening system. I have two questions.

First, the 5-year survival rate of gastric cancer from 1993 to 1995 was remarkably low at 43.9%. Is this low survival rate due to the cancer being diagnosed at an advanced stage? I think it is because there were many cases of advanced cancer, but this data does not tell us the stage of the cancer at the time of diagnosis.

Second, until 10 years ago, upper gastrointestinal imaging was the main method of gastric cancer preventive screening in Japan, but in Korea, endoscopy has already become mainstream. Could this difference in screening methods have led to the difference in mortality and morbidity rates between the two countries? Could you provide a comparative analysis of the data from the two countries?

Prof. Hidekazu Suzuki commented on two issues in the review article titled “Performance of the National Cancer Screening Program for Gastric Cancer in Korea.” [1]

The first issue is about the low 5-year survival rate for gastric cancer between 1993 and 1995 in Korea. The low 5-year survival rate for stomach cancer observed between 1993 and 1995 might indeed be due to the high incidence of advanced-stage diagnoses during that period. However, the data about gastric cancer stage is unavailable in the annual data from the Korean National Cancer Registry in 1990s. As described in the review article, the proportion of gastric cancers diagnosed in earlier stages (regional and localized stages) has increased after implementation of the National Cancer Screening Program for Gastric Cancer (NCSP-GC) in Korea [1]. Accordingly, 5-year survival rates for gastric cancer has increased owing to the NCSP-GC.

The radiographic screening using the upper gastrointestinal series (UGIS) has been a main modality in Japan because endoscopic screening was not recommended until 2014 [2]. Previous Japanese studies have reported an approximate 50% reduction in gastric cancer mortality associated with radiographic screening [2]. On the contrary, the revised Korean guideline for the NCSP-GC in 2015 did not recommend radiographic screening as a primary modality for screening [3], and a Korean study did not demonstrate a similar gastric cancer mortality reduction in participants who underwent UGIS [4]. Because of the different strategies for the screening modality selection, the main screening modality for the nationwide screening has been endoscopy in Korea and UGIS in Japan [5]. A synthetic control study reported inconsistent effects of nationwide gastric cancer screening programs on gastric cancer-related mortality in Korea and Japan; apparent benefits in Korea (estimated average postintervention rate ratios [RRs], 0.83; 95% confidence interval [CI], 0.71–0.96) and uncertain effects in Japan (RRs, 0.97; 95% CI, 0.88–1.07) [5]. However, this study did not directly compare the effects of the two nation’s screening programs and used insufficient data including covariates (H. pylori treatment, opportunistic screening, and socioeconomic status). Thus, further study is needed to compare the effectiveness according to screening modalities in nationwide gastric cancer screening programs between Korea and Japan.