Gastric cancer accounted for over one million new cases and 770,000 deaths globally in 2020, making it the sixth most common cancer worldwide. Although the overall incidence of gastric cancer has declined, the absolute number of cases is expected to rise due to an aging population, with projections indicating nearly 2 million new cases annually by 2040. The incidence of gastric cancer is highest in Asia, Latin America, and parts of Europe, with Helicobacter pylori (H. pylori) infection being a major environmental risk factor. Familial clustering and hereditary mutations account for only a small percentage of cases. Gastric adenocarcinoma is the most common histological type of gastric cancer, with non-cardia tumors being the predominant subtype.
Screening and Prevention of Gastric Cancer
To effectively reduce gastric cancer mortality, the Wilson and Junger criteria, established in 1968, provide a framework for developing screening programs. Key elements include the importance of the condition, its early symptomatic stage, and the availability of acceptable diagnostic tests and treatment. H. pylori infection plays a crucial role in the progression of gastric cancer, and its detection can be performed through non-invasive methods like urea breath tests, stool antigen tests, or serology. Eradication of H. pylori has been linked to reduced incidence of gastric cancer, particularly in areas where the prevalence of infection has decreased.
Screening Mechanisms
Three major approaches to gastric cancer screening have been identified: primary prevention, secondary prevention, and opportunistic screening. Primary prevention focuses on screening for H. pylori infection before preneoplastic lesions develop, and evidence suggests that early eradication significantly reduces gastric cancer risk. Secondary prevention targets individuals at higher risk due to pre-existing lesions, with endoscopic screening emerging as a more effective tool than radiographic methods. While endoscopic screening is resource-intensive, it provides higher sensitivity and the potential for early therapeutic intervention.
Emerging research also explores the role of serological markers, such as pepsinogen levels and H. pylori antibodies, as pre-screening tools to identify individuals who may benefit from endoscopy. Various scoring systems incorporating these markers, including the ABC and ABCD methods, show promise but have limitations in applicability across different populations.
Vaccination Against H. pylori
Despite extensive research on H. pylori, the development of an effective vaccine has proven challenging. Only one vaccine candidate has reached phase III clinical trials, but it has not achieved long-term protection. Given the early onset of H. pylori infection in childhood, a successful vaccine could have a substantial impact on global gastric cancer rates.
Recommendations from Different Societies
International organizations such as the International Agency for Research on Cancer (IARC) and the European Commission have emphasized the need for gastric cancer to be incorporated into national cancer control strategies, particularly in regions with high or intermediate cancer incidence. The Maastricht VI/Florence guidelines advocate for H. pylori screening and eradication in high-incidence regions, while the European Beating Cancer Plan seeks to implement population-based screening initiatives in Europe.
Screening Strategies in High and Intermediate-incidence Regions
Japan and Korea have long-established national gastric cancer screening programs. Japan, which introduced screening in the 1960s, has seen a 59% five-year survival rate due to its widespread use of endoscopic screening. Korea also employs endoscopy as the primary screening method, with biannual screenings recommended for individuals aged 40–75.
In Mainland China, opportunistic endoscopic screening is the primary method, particularly in high-risk rural areas. Taiwan has also investigated innovative strategies to reduce gastric cancer incidence through H. pylori screening and treatment.
Low-incidence Countries and Prevention Efforts
Countries like the United Kingdom and North America lack national screening programs, although guidelines do exist for targeted screening in high-risk individuals. There is growing evidence from observational studies that eradicating H. pylori in Western populations can reduce gastric cancer risk, though screening initiatives remain limited.
Future Research Developments
Ongoing research in Europe, including the Eurohelican and TOGAS studies, aims to evaluate the feasibility of gastric cancer screening programs across different member states. Longitudinal studies, such as the UK Helicobacter Pylori Screening Study and the GISTAR study in Latvia, will provide crucial insights into the long-term benefits of H. pylori eradication in reducing gastric cancer risk.
Conclusions
Although gastric cancer incidence is decreasing, disparities in screening programs persist, particularly between high-incidence regions in Asia and other parts of the world. National screening initiatives in Japan and Korea have significantly reduced gastric cancer mortality, but similar efforts are lacking in Europe and North America. Future research efforts and the implementation of evidence-based screening strategies are essential to reducing the global burden of gastric cancer.
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The study was recently published in the Cancer Screening and Prevention.
Cancer Screening and Prevention (CSP) publishes high-quality research and review articles related to cancer screening and prevention. It aims to provide a platform for studies that develop innovative and creative strategies and precise models for screening, early detection, and prevention of various cancers. Studies on the integration of precision cancer prevention multiomics where cancer screening, early detection and prevention regimens can precisely reflect the risk of cancer from dissected genomic and environmental parameters are particularly welcome.
