Overview and Risk Factors
Gastric cancer is the second most common malignancy worldwide and the 11th most common in the United States. Prevalence has been decreasing over the last century, likely due to better methods of food preservation. In addition, improved screening techniques-especially in Japan and other high-risk areas-have led to a decrease in mortality. Nonetheless, gastric cancer remains one of the most lethal malignancies, with the 5-year survival rate in the United States less than 20%.
More than 90% of cases are adenocarcinomas, which are derived from glandular tissue. The two general tumor types are intestinal and diffuse. In the intestinal type, which is more common, the tumors grow as discrete masses and eventually erode through the stomach wall into nearby organs. The diffuse type is less common overall, but is more prevalent in younger patients and carries a poorer prognosis. Diffuse tumors are poorly differentiated cancers with little cell cohesion. As a result, they grow outward along the submucosa of the stomach, widely enveloping the stomach without producing a discrete mass.
Tumors tend to be asymptomatic until the disease is advanced. The most common symptoms of advanced tumors are weight loss, early satiety, abdominal pain, nausea, and vomiting. Among the less common symptoms are dysphagia, melena, a palpable abdominal mass, and ascites.
Risk Factors
Incidence varies greatly by geographic area and race. Areas of highest incidence include Japan, Chile, and parts of Eastern Europe. African Americans, Asian Americans, and Latinos have a higher incidence than other demographic groups in the United States. Other risk factors are:
H. pylori infection. Chronic infection is a strong risk factor for gastric cancer of the distal stomach and may be responsible for up to 90% of distal gastric cancers.
Chronic gastritis, pernicious anemia, partial gastrectomy. A history of any of these conditions increases gastric cancer risk.
Genetics. A positive family history and blood type A are associated with an increased risk. The roles of specific genes are still unclear.
Gender. Males have twice the risk of females.
Diet. Factors strongly associated with an increased risk include high intake of salted, smoked, and pickled foods, and low intake of fruits and vegetables. (See Nutritional Considerations.)
Alcohol and tobacco use. Although both alcohol and tobacco use have long been considered risk factors, no conclusive evidence for their roles in gastric cancer has been demonstrated.
Age. The disease is rare before age 40, and the incidence increases steadily thereafter.
Diagnosis and Treatment
Diagnosis
In Japan, where there is a particularly high incidence of gastric cancer, mass screening programs of asymptomatic individuals using endoscopy or upper GI series identify early cases that may be curable with immediate treatment. As a result, survival rates have improved significantly. However, due to the relatively low incidence of gastric cancer in the United States, mass screening is not currently recommended.
Upper GI endoscopy with biopsy is diagnostic.
Barium swallow with upper GI series may reveal ulceration, mass, or distortion of the stomach wall. However, false negatives occur in up to 50%, especially with early gastric cancer cases. Subsequent biopsy is necessary for diagnosis.
CBC may show iron deficiency anemia.
CT scan and endoscopic ultrasound are used for staging and to evaluate for metastatic disease.
Treatment
Complete surgical resection offers the only hope for cure. Unfortunately, most tumors are already advanced at diagnosis and not amenable to full resection. Total or subtotal gastrectomy is indicated for tumors confined to the stomach. Resection of adjacent organs may be required if the tumor has spread.
Early detection of gastric cancer may improve patient survival. Patients may elect to be treated with endoscopic mucosal resection, a low-cost and relatively safe alternative to surgery.1
Surgery, chemotherapy, or radiation may be used for palliation.
Nutritional Considerations
Stomach cancer is associated with the carcinogenic effect of nitrosamines, compounds derived from nitrates that are used to preserve meats. High sodium intakes appear to be responsible for the high rates of gastric cancer in cultures where processed (salted) fish and soy foods are consumed frequently. In epidemiologic studies, a protective effect has been noted for plant-rich diets, especially those high in fruits, vegetables, and whole grains.2 Consumption of these foods is inversely related to stomach cancer mortality.3 In observational studies, the following dietary factors are associated with reduced risk:
Avoidance of animal products, particularly those containing nitrates. Cholesterol and animal protein intakes are associated with several subtypes of gastric and esophageal cancer.4 Nitrate-containing red meat and processed meat increase the risk for gastric cancer 3-fold, and frequent intakes of dairy products and fish are also associated with increased risk.5 In persons with a family history of gastric cancer and high red meat consumption, the risk for gastric cancer is roughly 25 times that of individuals with no history and low meat intake.6 Red meat contains particularly high levels of heme iron; individuals taking in the highest amount of this nutrient had roughly three times the risk for upper digestive tract cancer (predominantly gastric cancer) as those consuming the lowest amount.7
Eating more fruits and vegetables. Fruit intake is inversely related to gastric cancer incidence, and high vegetable consumption is associated with up to a 30% reduction in risk compared with low intakes.8 These apparent anticancer effects may be attributed to 3 factors: the inhibiting effect of vitamin C and other antioxidants on nitrosamine formation; the effects of carotenoids,9 flavonoids,10 and sulfur compounds in Allium species of vegetables, including garlic and onion;11 and the total antioxidant potential of the diet, particularly in H. pylori-infected persons.12
Replacing refined grains with whole grains. Whole grain and dietary fiber intake are associated with greatly reduced risk for gastric cancer.13,14 In contrast, several reports show that high consumption of carbohydrates from refined grain products increases risk,15,16 possibly because fruit and vegetable consumption may be lower in these cases.17
Avoiding highly salted foods. Sodium is a gastric irritant, and table salt intake is associated with gastric cancer risk, especially in Asians, who frequently eat salted fish,18 processed or salted foods,19 and fermented soy foods with added sodium.20
Maintenance of a healthy body weight. Obesity is a risk factor for adenocarcinoma of the gastric cardia and esophagus. Persons with a higher body mass index (BMI) have 2 to 4 times the risk of those with lower BMI, and the most obese have nearly 9 times the risk.21,22 (See Obesity chapter.)
Diet and survival in gastric cancer. Although the role of diet in gastric cancer prognosis needs further study, data indicate that patients whose diets were lower in animal fat, animal protein, and nitrosamines before diagnosis had approximately half the risk of death from this cancer, compared with other patients.23
Orders
See Basic Diet Orders chapter.
Limit intake of salted and pickled foods.
Avoid foods preserved with nitrates.
What to Tell the Family
Diet plays a critical role in the prevention of gastric cancer, which remains one of the leading causes of cancer-related death worldwide. Animal products, especially those preserved with nitrates, are associated with increased risk of gastric cancer and other cancers. A diet that includes regular servings of fruits, vegetables, and whole grains may reduce that risk, in addition to its other health benefits. The whole family would do well to incorporate these dietary changes into their lifestyle.
References
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2. McCullough ML, Robertson AS, Jacobs EJ, Chao A, Calle EE, Thun MJ. A prospective study of diet and stomach cancer mortality in United States men and women. Cancer Epidemiol Biomarkers Prev. 2001;10:1201-1205.
3. Ocke MC, Bueno-de-Mesquita HB, Feskens EJ, Kromhout D, Menotti A, Blackburn H. Adherence to the European Code Against Cancer in relation to long-term cancer mortality: intercohort comparisons from the Seven Countries Study. Nutr Cancer. 1998;30:14-20.
4. Mayne ST, Risch HA, Dubrow R, et al. Nutrient intake and risk of subtypes of esophageal and gastric cancer. Cancer Epidemiol Biomarkers Prev. 2001;10:1055-1062.
5. Ward MH, Lopez-Carrillo L. Nutrient intake and gastric cancer in Mexico. Int J Cancer. 1999;83:601-605.
6. Palli D, Russo A, Ottini L, et al. Red meat, family history, and increased risk of gastric cancer with microsatellite instability. Cancer Res. 2001;61:5415-5419.
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15. Jedrychowski W, Popiela T, Steindorf K, et al. Nutrient intake patterns in gastric and colorectal cancers. Int J Occup Med Environ Health. 2001;14:391-395.
16. Chatenoud L, La Vecchia C, Franceschi S, et al. Refined-cereal intake and risk of selected cancers in Italy. Am J Clin Nutr. 1999;70:1107-1110.
17. Jansen MC, Bueno-de-Mesquita HB, Rasanen L, et al. Consumption of plant foods and stomach cancer mortality in the seven countries study. Is grain consumption a risk factor? Seven Countries Study Research Group. Nutr Cancer. 1999;34:49-55.
18. Tsugane S, Sasazuki S, Kobayashi M, Sasaki S. Salt and salted food intake and subsequent risk of gastric cancer among middle-aged Japanese men and women. Br J Cancer. 2004;90:128-134.
19. Ji BT, Chow WH, Yang G, et al. Dietary habits and stomach cancer in Shanghai, China. Int J Cancer. 1998;76:659-664.
20. Wu AH, Yang D, Pike MC. A meta-analysis of soyfoods and risk of stomach cancer: the problem of potential confounders. Cancer Epidemiol Biomarkers Prev. 2000;9:1051-1058.
21. Lagergren J, Bergstrom R, Nyren O. Association between body mass and adenocarcinoma of the esophagus and gastric cardia. Ann Intern Med. 1999;130:883-890.
22. Chow WH, Blot WJ, Vaughan TL, et al. Body mass index and risk of adenocarcinomas of the esophagus and gastric cardia. J Natl Cancer Inst. 1998;90:150-155.
23. Palli D, Russo A, Saieva C, Salvini S, Amorosi A, Decarli A. Dietary and familial determinants of 10-year survival among patients with gastric carcinoma. Cancer. 2000;89:1205-1213.
