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Gastric cancer describes a broad mix of malignant neoplasms derived from the different histological components that make up the stomach. These include adenocarcinoma, lymphoma, carcinoid, and sarcoma. Gastric adenocarcinoma accounts for over 90% of all cases of gastric cancers globally.1,2 The incidence of gastric cancer decreased dramatically in the latter half of the 20th century; however, a recent rise in proximal gastric cancer incidence has been noted. Gastric cancer remains the second leading cause of cancer-related deaths worldwide (Fig. 22-1).1–4 As is the case for many cancers, the epidemiological distribution of gastric cancer demonstrates a marked variation in regional incidence—with as much as a 10-fold difference between the highest- and lowest-risk populations.5 An estimated 900,000–950,000 newly diagnosed gastric cancer cases per year occurred worldwide at the beginning of the 21st century, with the great majority of these cases found in developing countries and China.2,3,5–7 Industrialized nations continue to see a marked decline in the incidence of gastric cancer, particularly in the body and antrum. In the United States, the estimated number of new cases diagnosed in 2009 was 21,130 with the number of gastric cancer–associated deaths estimated to be 10,620.7 These numbers highlight the continued decreasing trend in both gastric cancer incidence and mortality (Table 22-1). In fact, death rates attributed to gastric cancer in the Unites States fell by over 40% for males and 32% for females between the years 1990 and 2005.7
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The diagnosis of gastric cancer portends a poor prognosis with reported overall 5-year survival rates between 20 and 25% in most industrialized nations.1,6,8 Stage of disease at time of diagnosis is clearly one of the most important correlates of cancer survival. Patients diagnosed with earlier stages of gastric cancer have a distinct advantage in 5-year survival compared to those with more advanced-stage disease (Fig. 22-2). Although the 5-year survival rate for all cases of gastric cancer in the United States between the years 1996 and 2004 was 25%, it was as little as 3% for patients with distant disease and as high as 61% for those who had only localized disease at time of diagnosis.7 The survival advantage of early diagnosis is best exemplified by Japan's overall 5-year gastric cancer survival rate of 52%. ...