Since much is unknown about factors that lead to progression of the pre-neoplastic lesions and cancer. In addition, there is ongoing debate on the optimal surveillance intervals and techniques. To solve these important clinical questions, the establishment of a registry for a longitudinal study is planned.

Helicobacter pylori is believed to affect more than half of the world's population and is thought to affect nearly 2 million people in Hong Kong alone. It is a major cause of peptic ulcer disease and is implicated in the pathogenesis of the majority of gastric cancers. Since 1994, the World Health Organization has designated H. pylori infection as a class 1 carcinogen. Gastric cancer was the sixth commonest malignancy in Hong Kong in 2015; it was also the second commonest cause of death from cancer in Asia. It is thought that chronic inflammation of the gastric mucosa caused by H. pylori progresses to pre-neoplastic lesions, namely atrophic gastritis and intestinal metaplasia, before developing into frank dysplasia and carcinoma. Successful H. pylori eradication can lead to a rapid decrease in active inflammation, with early treatment effective in preventing the progression of disease. It is believed that atrophic gastritis may be reversible, whereas intestinal metaplasia has passed the point of no return and unlikely to have regression. National screening programmes in both Japan and Korea recommend endoscopy for all men and women over 40 years of age with several uncontrolled trials suggesting that this has led to a reduction of mortality due to gastric cancer. However, in countries with a lower incidence of gastric cancer, this population-based approach may not be cost-effective. Much is unknown about factors that lead to progression of the pre-neoplastic lesions and cancer. In addition, there is ongoing debate on the optimal surveillance intervals and techniques. To solve these important clinical questions, the establishment of a registry for a longitudinal study is planned.

Inclusion Criteria:

• Adults >= 18 years of age
• Written informed consent obtained
• Diagnosed with current or past H. pylori infection,
• Histologically proven atrophic gastritis (body and/or antrum of stomach), intestinal metaplasia (complete and incomplete), dysplasia (any grade) and/or gastric cancer (post- treatment)

Exclusion Criteria:

• Co-morbid illness that prohibit endoscopic surveillance
• Declines for study questionnaire, biobanking of specimens and/or regular review per study protocol

Inclusion Criteria

1. Adults >= 18 years of age
2. Written informed consent obtained
3. Diagnosed with current or past H. pylori infection,
4. Histologically proven atrophic gastritis (body and/or antrum of stomach), intestinal metaplasia (complete and incomplete), dysplasia (any grade) and/or gastric cancer (post-treatment)

Exclusion Criteria

1. Co-morbid illness that prohibit endoscopic surveillance
2. Declines for study questionnaire, biobanking of specimens and/or regular review per study protocol