Nordic Gastric and Esophageal Tumor Study

This is a population-based case-control study in all 5 Nordic countries from 1994 onwards. Cases with esophageal or gastric cancer will be compared with 10 times as many population controls. The project includes a specific study "Long-term medication with proton pump inhibitors and risk of gastric cancer", which is summarized here: Research question: Medication with proton pump inhibitors (PPI) is a most commonly used drug, prompted by its good anti-acidic efficacy and short-term safety profile. Gastric cancer is the 3rd leading cause of cancer-related mortality globally, responsible for 770,000 deaths each year. There are biological mechanisms linking long-term PPI-use with an increased risk of gastric cancer. But existing research has not provided a definite answer to whether long-term PPI-use increases risk of gastric cancer. The literature is hampered by short follow-up time, insufficient statistical power, lack of population-based design and confounding. With the availability of nationwide complete drug registries in the Nordic countries, the first two starting in 1994 (Denmark and Finland), we can now, by adding registry data from all Nordic countries, conduct the first study providing a robust and valid answer to this research question. Overarching aim To clarify if (and if so to what extent) long-term PPI-therapy increases the risk of gastric adenocarcinoma. For validation reasons, we will also examine how long-term use of histamine-2-receptor blockers (H2RB) influences the risk of developing gastric adenocarcinoma. These analyses will validate that the findings are specific for PPIs. H2RB are used for the same indications as PPIs, but with a different biological mechanism. Hypothesis Long-term use of PPI (but not H2RB) increases the risk of gastric adenocarcinoma. Prerequisites This will be the first project with all prerequisites to provide conclusive answers to the hypotheses above, i.e.: * Long follow-up (up to 28 years) * Complete follow-up (by virtue of the nationwide complete Nordic registries) * Population-based design (which rules out biased selection of cases or controls) * Sufficient statistical power (all five Nordic countries participate with nationwide data) * High-quality data on exposures, outcomes and confounders (thanks to well-maintained and complete nationwide Nordic health data registries) * Control for confounding factors (available for all participants, both cases and controls)

Sex

All

Minimum age

18 Years

Inclusion Criteria:

* Diagnosis of esophageal or gastric tumor or frequency matched population control participants

Exclusion Criteria:

* Age below 18 years