Epidemiology of Gastric Cancer

Gastric cancer ranks as the fifth most frequently diagnosed cancer globally and is the fourth leading cause of cancer deaths worldwide. The disease shows striking differences in how common it is depending on where people live. In regions like East Asia—especially Japan and Mongolia—and parts of Eastern Europe, gastric cancer occurs much more frequently than in other parts of the world. In contrast, countries in Northern Europe and North America, including the United States, report much lower rates, similar to those seen in many African regions.^[1][2]

In the United States specifically, gastric cancer accounts for only about 1.5% of all newly diagnosed cancers each year. The overall number of new cases has been steadily declining over the past several decades, dropping by approximately 1.5% annually over the last ten years. This downward trend is believed to be linked to improved food storage methods, such as refrigeration, which has reduced reliance on preserved and salted foods. Despite this encouraging decline, an estimated 30,300 new cases and 10,780 deaths from gastric cancer are expected in the U.S. in 2025.^[1][5][11]

However, not all age groups are experiencing the same trends. While older adults continue to see declining rates, younger adults—those between 25 and 39 years old—have seen an increase in gastric cancer diagnoses since the late 1970s. The reasons behind this rise in younger populations are not yet fully understood and require further investigation. Additionally, gastric cancer does not affect all demographic groups equally. In the United States, the disease is more common among Hispanic, Black, and Asian/Pacific Islander populations compared to white Americans.^[3][11][21]

Men are nearly twice as likely as women to develop gastric cancer. The average age at diagnosis is 68, with about 60% of cases occurring in people aged 65 or older. This means that gastric cancer primarily affects older individuals, though it can occur at any age.^[1][3]

Causes of Gastric Cancer

Gastric cancer develops when a genetic mutation—a change in the DNA of stomach cells—causes those cells to grow out of control instead of dying off as they normally would. Over time, these rapidly multiplying cells accumulate and form a tumor. If left untreated, the cancer cells can invade deeper layers of the stomach wall and eventually spread to nearby organs such as the liver, pancreas, or lungs, or even to distant parts of the body through a process called metastasis.^[2][3]

Researchers do not know exactly what triggers these genetic mutations, but they have identified several factors that significantly increase the risk of developing gastric cancer. One of the most important is infection with a bacterium called Helicobacter pylori, or H. pylori. This common infection can inflame and damage the stomach lining over many years, leading to changes that may eventually turn into cancer. Many people with H. pylori infections do not have symptoms, but some develop chronic inflammation of the stomach, known as atrophic gastritis, which is a known precursor to cancer.^[1][3][11]

Another virus, the Epstein-Barr virus, has also been associated with an increased risk of gastric cancer. Certain chronic conditions such as gastroesophageal reflux disease (GERD)—where stomach acid frequently backs up into the esophagus—can also contribute to cancer development over time. People with a history of stomach ulcers, stomach polyps, or a condition called pernicious anemia (where the body cannot absorb enough vitamin B12) are also at higher risk.^[1][11]

Some inherited genetic conditions also raise the likelihood of developing gastric cancer. These include familial adenomatous polyposis, Lynch syndrome, and hereditary diffuse gastric cancer syndrome, among others. Having a close family member who has had gastric cancer increases your own risk, even if no specific genetic syndrome has been identified.^[1][11]

Risk Factors for Gastric Cancer

Several habits, behaviors, and medical conditions can increase a person’s risk of developing gastric cancer. One of the most significant controllable risk factors is diet. Eating a lot of salty, smoked, pickled, or highly processed foods has been linked to higher rates of stomach cancer. On the other hand, a diet that is low in fresh fruits and vegetables may also increase risk, as these foods contain nutrients and compounds that help protect the stomach lining from damage.^[1][11]

Smoking cigarettes, vaping, or chewing tobacco significantly raises the risk of gastric cancer. Similarly, drinking too much alcohol over a long period of time can damage the stomach lining and contribute to cancer development. Obesity is another modifiable risk factor; carrying excess weight has been associated with a higher likelihood of developing several types of cancer, including gastric cancer.^[1][3][21]

Occupational and environmental exposures also play a role. People who work with or are frequently exposed to substances like coal, metal, or rubber may be at increased risk. These exposures can damage cells over time and contribute to the development of cancer.^[1]

Certain pre-existing medical conditions can also raise risk. Chronic inflammation of the stomach lining, especially a condition called intestinal metaplasia—where normal stomach cells are replaced by cells that resemble those of the intestines—is a known risk factor. People with autoimmune atrophic gastritis, where the immune system attacks the stomach’s own cells, are also at elevated risk.^[1][11]

Finally, advanced age is a major non-modifiable risk factor. The majority of gastric cancer cases occur in people over 65, and the disease is more common in men than in women. Ethnicity also plays a role, with higher rates observed in certain populations, as previously mentioned.^[1][3]

Symptoms of Gastric Cancer

One of the challenges with gastric cancer is that it often does not cause noticeable symptoms in its early stages. When symptoms do appear, they are frequently vague and can easily be mistaken for other, less serious digestive problems. This lack of early warning signs means that many people are not diagnosed until the cancer has progressed to a more advanced stage, which complicates treatment and reduces survival rates.^[1][3]

Common early symptoms of gastric cancer include unexplained weight loss and persistent stomach pain, often felt above the belly button. Many people experience frequent indigestion, heartburn, and a feeling of fullness or bloating even after eating only a small amount of food. Loss of appetite is also very common, and some people feel too full to eat regular-sized meals.^[1][3]

As the disease progresses, symptoms can become more severe. People may develop nausea and vomiting, sometimes bringing up blood. Stools may appear black or tarry due to bleeding in the stomach. Difficulty swallowing can occur if the tumor is located near the junction where the esophagus meets the stomach. Fatigue and weakness are also common, often resulting from anemia caused by slow, chronic bleeding from the tumor.^[1][3]

In some cases, advanced gastric cancer may cause a noticeable mass in the abdomen that a doctor can feel during a physical exam. Jaundice—a yellowing of the skin and eyes—can develop if the cancer spreads to the liver.^[1][3]

Many of these symptoms overlap with those of other, more common conditions such as ulcers or gastritis. However, if symptoms persist or worsen, it is important to see a healthcare provider for evaluation. Early detection, even when symptoms are vague, can improve outcomes significantly.^[1][3]

Prevention of Gastric Cancer

While not all cases of gastric cancer can be prevented, there are several steps people can take to reduce their risk. One of the most effective measures is treating H. pylori infection if it is detected. Antibiotics can eliminate this bacterium and reduce the chronic inflammation and damage to the stomach lining that it causes. In regions where H. pylori is common, public health programs aimed at identifying and treating infections have contributed to lower rates of gastric cancer.^[1][21]

Dietary changes can also play a significant role in prevention. Eating a diet rich in fresh fruits and vegetables provides the body with antioxidants and other protective compounds that help guard against cancer. Reducing intake of salty, smoked, pickled, and processed foods can lower risk. Using refrigeration for food storage instead of relying on salting or smoking as preservation methods is one reason gastric cancer rates have declined in many developed countries.^[1][11][21]

Avoiding tobacco in all its forms—cigarettes, cigars, chewing tobacco, and vaping—is another important preventive measure. Similarly, limiting alcohol consumption can reduce the risk of stomach damage and cancer development. Maintaining a healthy weight through regular physical activity and a balanced diet also helps lower risk.^[1][21]

For people with a family history of gastric cancer or known genetic syndromes that increase risk, regular screening and close monitoring by a healthcare provider may be recommended. While there is no standard screening test for gastric cancer in the United States, people at high risk may benefit from periodic endoscopy—a procedure in which a flexible tube with a camera is inserted through the mouth to visually inspect the stomach lining.^[2][8]

In countries where gastric cancer is much more common, such as Japan and South Korea, mass screening programs using endoscopy have been successful in detecting cancer at earlier, more treatable stages. These programs have contributed to improved survival rates in those regions.^[2][13]

Pathophysiology of Gastric Cancer

The development of gastric cancer is a gradual process that typically unfolds over many years. It begins with small changes in the DNA of cells in the stomach lining. These changes, or mutations, cause cells to multiply more rapidly than they should and to avoid the normal process of cell death. As these abnormal cells accumulate, they form clusters and eventually develop into a tumor.^[1][3]

In the earliest stages, cancer cells are confined to the innermost layer of the stomach, called the mucosa. This stage is sometimes referred to as carcinoma in situ. At this point, the cancer has not yet invaded deeper layers of the stomach wall and is often easier to treat successfully. However, because there are usually no symptoms at this stage, it is rarely detected unless a person undergoes screening for other reasons.^[2][9]

As the cancer progresses, it grows deeper into the stomach wall, invading the muscular layers and eventually reaching the outer layer. The tumor may also spread to nearby lymph nodes, which are small structures that help filter out harmful substances. Once cancer cells reach the lymph nodes, they can travel through the lymphatic system to other parts of the body.^[2][3]

In advanced stages, gastric cancer can metastasize to distant organs such as the liver, lungs, or bones. This spread significantly complicates treatment and reduces the chances of a cure. The five-year survival rate for gastric cancer that has spread to distant sites is much lower than for cancer that is caught early and confined to the stomach.^[2][11]

Gastric cancers are often classified based on their location in the stomach and their appearance under a microscope. In the United States, most gastric cancers develop in the upper part of the stomach, near where it connects to the esophagus. This area is called the gastroesophageal junction. In other parts of the world, cancer more commonly develops in the lower part of the stomach, known as the antrum or body.^[1][2]

Under the microscope, gastric adenocarcinomas are divided into two main types: intestinal and diffuse. Intestinal-type cancers tend to grow more slowly and have cells that look relatively similar to normal stomach cells. Diffuse-type cancers, on the other hand, grow and spread more quickly and have cells that look very different from normal cells. Diffuse cancers are generally harder to treat and have a poorer prognosis.^[2][5]