CommentaryGastric cancer epidemiology and risk factors
Introduction
The second half of the 20th century has seen a sharp worldwide decline in both the incidence and mortality of gastric cancer. Despite this, the condition remains the world's second leading cause of cancer mortality behind lung cancer. It has been estimated that there will have been more than 870,000 deaths from the disease in the year 2000, accounting for approximately 12% of all cancer deaths 1, 2, 3.
Gastric cancer has attracted much attention from epidemiologic investigators over recent years, particularly with the emergence of H. pylori as a risk factor for the condition. This has lead to an improved understanding of the etiology and pathogenesis of gastric cancer and raised the possibility of active prevention of the disease. Differences in exposures to H. pylori and a range of other environmental factors probably account for much of the variations seen in the incidence of gastric cancer over time and between populations.
We begin with a discussion of the pathology of gastric cancer, then consider descriptive epidemiology, and finally review the evidence concerning possible etiologic factors. The evidence described in this report was identified from the English language literature by searching the Medline database.
Section snippets
Pathology
Approximately 90% of stomach cancers are adenocarcinomas. Non-Hodgkin's lymphomas and leiomyosarcomas make up most of the remaining 10%.
Adenosquamous, squamous, and undifferentiated carcinomas also occur but are rare. Other very rare malignant primary tumors of the stomach include choriocarcinomas, carcinoid tumors, rhabdomyosarcomas, and hemangiopericytomas. Kaposi's sarcoma, in association with the acquired immunodeficiency syndrome, has also been reported [4].
Adenocarcinomas may be
Descriptive epidemiology
One of the notable features of the descriptive epidemiology concerning gastric cancer is that it establishes some clear distinctions between cancer localized to the gastric cardia and cancer of the rest of the stomach, as discussed below.
H. pylori
Since H. pylori was first reported by Marshall in 1983, a wealth of evidence has been gathered concerning this organism and its role in the etiology of gastric cancer [25]. In 1994, the International Agency for Research on Cancer classified H. pylori as carcinogenic to humans [26]. Evidence supporting a causal association between H. pylori and gastric cancer can be found in ecologic studies, case–control studies, and prospective cohort studies.
An international population study performed by the
Conclusions
Although much is known about the causes of gastric cancer, much still is shrouded in mystery. Particularly puzzling is the recent rise in adenocarcinoma around the cardia, largely confined to White males in affluent societies. One thing is clear. Contrary to a developing view that H. pylori is a major cause of gastric cancer, simple epidemiologic analysis shows that it is probably a minority cause in Western societies. If chronic H. pylori infection increases the risk of cancer by a factor of
Acknowledgments
The views presented in this article are those of the authors and are not intended to represent those of the Commonwealth Department of Veterans' Affairs or the Repatriation Medical Authority of the Commonwealth of Australia.
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