Gastric adenocarcinoma is the most common cancer of the stomach and one of the leading causes of cancer death worldwide. Roughly 1.03 million new cases and about 780,000 deaths are estimated each year, which places it third among cancers by mortality. The risk is far from uniform: where a person lives, their sex and the period in which they are diagnosed all change how likely the disease is, and those differences decide who is screened and who receives preventive treatment.
Where the cancer is common
The highest incidence is in East Asia, with China, Korea and Japan at the top; eastern European countries and Chile are also high-incidence regions. Incidence is almost twice as high in men as in women.
How the site of disease has shifted
A century ago, around the 1920s, gastric adenocarcinoma was among the most common cancers in the United States. Its incidence then decreased gradually, for reasons that were never defined but are believed to include the introduction of refrigeration of foods in place of preservatives. In 2020, about 27,000 cases of gastric adenocarcinoma were diagnosed in the United States, and about 11,000 of those patients died.
In Western countries the incidence of cancers of the body and distal stomach has continued to fall, while cancers of the gastroesophageal junction have increased over recent years. One suspected contributor is the higher use of nitrate in salted, smoked or dried foods. Another is the chronic inflammation from gastroesophageal reflux disease (GERD), especially in obese people; H. pylori infection is also suspected.
Prevention by treating H. pylori
H. pylori eradication lowers the incidence of gastric cancer in asymptomatic infected people. Treating an asymptomatic H. pylori infection has been shown to significantly reduce the incidence of gastric cancer in particular groups: patients with a first-degree family member with a history of gastric cancer, and patients with a prior early-onset gastric cancer. In these patients, eradication therapy for H. pylori is suggested to prevent cancer.
Inherited risk genes
Some inherited genes are associated with a higher chance of gastric cancer progression:
- a mutation of CDH1, which is also a risk factor for lobular breast cancer
- a germline mutation in a mismatch repair gene, which causes Lynch syndrome
- familial conditions such as familial adenomatous polyposis, juvenile polyposis and Peutz-Jeghers syndrome
One hypothesis proposes that gastric cancer stem cells originate from the bone marrow, and that H. pylori has an important role in forming these stem cells from the bone marrow. This is still under study.
Surveillance
The surveillance program for gastric cancer depends on the region. If the region is considered high-incidence, endoscopy of the upper gastrointestinal tract and serum pepsinogen testing can be performed, as is done in South Korea and Japan. In low-incidence countries such as the United States, performing endoscopy in all asymptomatic individuals is not cost-effective. The exception in the United States is the asymptomatic patient with a CDH1 mutation.