In the United States, gastric cancer accounts for 1.6% of all cancers with an estimated 27,510 cases in 2019 per the SEER database. Although the incidence of gastric cancer has been decreasing in the United States, there have been alarming trends, suggesting an increased rate in select populations, especially in the young Hispanic population in the age group of 20-49 years ().
Risk factors for gastric cancer include increasing age, male sex, presence of intestinal metaplasia, and varying degrees of dysplasia (Endoscopy. 2019;51:365-88). Gastric cancer is primarily characterized into two subtypes: intestinal type, which is the more common type associated with gastric intestinal metaplasia (GIM), and the diffuse type, which is genetically determined.
GIM, a precancerous lesion, is defined as the replacement of the normal gastric mucosa by intestinal epithelium and can be limited (confined to one region of the stomach) or extensive (involving more than two regions of the stomach). Risk factors for GIM include Helicobacter pylori infection, age, smoking status, and presence of a first-degree relative with gastric cancer. Histologically, GIM is characterized as either complete – defined as the presence of small intestinal-type mucosa with mature absorptive cells, goblet cells, and a brush border – or incomplete – with columnar “intermediate” cells in various stages of differentiation, irregular mucin droplets, without a brush border. Extensive and incomplete type of GIM is associated with a higher risk of gastric cancer ().
Gastric cancer screening has been shown to be effective in countries with a high incidence of gastric cancer. However, in low-incidence countries, at-risk patients can be identified based on epidemiology, genetics, and environmental risk factors as well as incidence of H. pylori, and serologic markers of chronic inflammation such as pepsinogen, and gastrin (). H. pylori eradication has been shown to reduce the risk of developing gastric adenocarcinoma in patients with H. pylori-associated GIM. For detection of dysplasia and early gastric cancer, patients with GIM should undergo a full systematic endoscopy protocol of the stomach with clear photographic documentation of gastric regions and pathology.
On standard white-light endoscopy, GIM appears as small gray-white, slightly elevated plaques surrounded by mixed patchy pink and pale areas of mucosa causing an irregular uneven surface. Sometimes GIM can present as patchy erythema with mottling.
On the other hand, presence of features such as differences in color, loss of vascularity, elevation or depression, nodularity or thickening, and abnormal convergence or flattening of folds should raise suspicion for gastric dysplasia or early gastric cancer. Presence of GIM on endoscopy should be documented in detail with photographic evidence including the location and extent of GIM, and obtaining mapping biopsies that include at least two biopsies from the antrum (from lesser and greater curve) and from the body (lesser and greater curve). Endoscopic surveillance is recommended every 3 years in patients with extensive GIM affecting the antrum and body, incomplete GIM, and a family history of gastric cancer.
This is a summary provided by the moderator of one of the AGA Postgraduate Course sessions held at DDW 2019. Dr. Sharma is professor of medicine and director of fellowship training, division of gastroenterology and hepatology, University of Kansas, Kansas City.