Gastric Cancer: Overview and Symptoms

Gastric cancer is the second most common cancer in the world and the 11th most common in the United States. It is most common in Japan, Chile, and parts of Eastern Europe. In the U.S., it affects African-Americans, Asian-Americans, and Latinos more commonly than other demographic groups.

The number of cases has been decreasing steadily over the last century. This is likely due to better methods of food preservation, including refrigeration. Nonetheless, gastric cancer remains one of the most lethal cancers, with a five-year survival rate in the United States of less than 20 percent.

In Japan, where there is a particularly high incidence of gastric cancer, screening programs of all adults are used to identify early cases. As a result, survival rates in Japan have improved significantly. However, due to the relatively low incidence of gastric cancer in the United States, mass screening is not currently available.

Symptoms

• Tumors generally cause no symptoms until the disease is advanced.
  
• When symptoms occur, the most common are weight loss, abdominal pain, nausea, vomiting, decreased appetite, and a feeling of fullness in the stomach.
  
• Less common symptoms include difficulty swallowing, black stools, a noticeable abdominal mass, and fluid in the abdomen (called ascites).

Risk Factors

• Helicobacter pylori infection: Chronic infection with the Helicobacter pylori bacteria (the same bacteria that contributes to peptic ulcers) is a strong risk factor for gastric cancer. Some studies suggest that these bacteria may be responsible for up to 90 percent of gastric cancers.
  
• Age: The disease is rare before age 40, but the incidence increases steadily thereafter.
  
• Genetics: A positive family history and blood type A are associated with an increased risk. It is unclear if there are specific genes that increase or decrease the risk.
  
• Gender: Males have twice the risk, compared with females.
  
• Diet: High dietary intake of salted, smoked, and pickled foods is known to increase risk. Higher intake of fruits and vegetables lower the risk.
  
• Alcohol and tobacco use: Alcohol and tobacco use are thought to increase the risk, but there is not yet conclusive evidence for their roles.
  
• Diseases of the stomach: A history of chronic gastritis, pernicious anemia, or partial gastrectomy increases the risk.

Diagnosis

• A thorough history and physical examination are the first steps of the evaluation for gastric cancer.
  
• The best test for diagnosis is endoscopy with biopsy. After administration of anesthesia, a small fiberoptic cable is slowly placed down the throat into the stomach. This allows for direct visualization of the stomach walls and biopsy of the suspected tumor.
  
• A commonly used test, called an upper GI series with barium swallow, involves a series of X-rays to evaluate the stomach and upper intestines. Before the test, patients must drink a small amount of a contrast agent to improve the accuracy of the X-ray pictures.
• In some cases, a CT scan or other testing may be necessary.

Treatment

• Surgery to remove the tumor is essential for cure. In the early stages of the disease, surgery has a good success rate. Unfortunately, most tumors are already advanced at diagnosis and cannot be completely removed.
  
  In some cases, a part of the stomach is removed (partial gastrectomy). In others, the entire stomach must be removed (gastrectomy). In still others, nearby organs must also be removed.
• Chemotherapy or radiation may be used in patients with severe symptoms, but they will not cure the disease.

Nutritional Considerations for Prevention

In research studies, the following nutritional steps are associated with reduced risk of gastric cancer:

• Avoidance of animal products: Animal products contain several cancer-causing compounds that increase the risk for gastric cancer. People who have a strong family history of gastric cancer and who eat high amounts of red meat appear to have nearly 25 times increased risk of the disease, compared to other individuals.
  
  In particular, it is wise to avoid animal products that contain nitrates. Nitrate-containing red meat and processed meat increase the risk for gastric cancer threefold. Nitrates are used as a preservative in many types of meat. They can result in the formation of nitrosamines, which are known carcinogens.
  
  Further, cholesterol and animal protein intakes are associated with several subtypes of gastric and esophageal cancer. Red meat also contains particularly high levels of heme iron, which may increase the risk of digestive tract cancers, including gastric cancer.
  
• A diet high in fruits and vegetables: Increased fruit and vegetable intake is associated with reduced risk of gastric cancer. This may be due to the high amounts of antioxidants, decreasing the formation of nitrosamines.
  
• Replacing refined grains with whole grains: Whole grain and dietary fiber intake are associated with a greatly reduced risk of gastric cancer. In contrast, several reports show that high consumption of carbohydrates from refined grain products increases risk, possibly because fruit and vegetable consumption may be lower in these cases.
  
• Avoidance of highly salted foods: Sodium is a stomach irritant. High use of table salt is associated with gastric cancer risk, especially in Asians, who frequently eat salted fish, processed or salted foods, and fermented soy foods with added sodium.
  
• Maintenance of a healthy body weight: Overweight people have two to four times the risk of developing gastric cancer, compared with people of normal weight. The most obese people have nearly nine times the risk.
  
  A plant-based diet is not only free of cholesterol and animal fat; it is also helpful for losing weight. The best choices are whole grains, vegetables, fruits, and beans, without added oils. In research studies using plant-based diets, weight loss averages about one pound per week. For more information, see How to Achieve a Healthy Weight. Be sure to take a multiple vitamin to ensure that your diet includes vitamin B₁₂.
  

Nutritional Considerations for Survival

• Patients diagnosed with gastric cancer whose diets are lower in animal meats have improved survival odds compared with patients with unrestricted diets.