Gastric cancer.

Abstract

Most countries with adequate statistical infrastructure have registered declines in gastric cancer mortality and incidence rates. Such a trend is dominated by the most frequent variant, namely the so-called intestinal type of adenocarcinoma, usually ulcerated and occupying predominantly the antrum and the antrum-corpus junction. This variant is considered the endstage of a prolonged precancerous process with gradual progression from (a) chronic active gastritis to (b) multifocal atrophic gastritis to (c) intestinal metaplasia, first resembling the phenotype of the small intestine and later that of the colon, to (d) dysplasia and (e) finally to invasive carcinoma. Major trends in dietary habits, namely lower intake of salt and increased and more frequent consumption of fresh fruits and vegetables, have been linked to the decline. In parallel with those trends, improved sanitation and more adequate housing may be responsible for the declining rates of infection with Helicobacter pylori, the major cause of chronic active gastritis. A decline in the frequency of papillary adenocarcinoma of the oxyntic mucosa, associated with the pernicious anaemia syndrome, appears to have taken place much earlier. Although the frequency of the pernicious anaemia syndrome seems to have remained at similar levels, its complications in terms of papillary adenocarcinoma have decreased in populations of northern European extraction. This may be related to time trends in dietary habits. The secular decline in diffuse carcinoma has been either of much less magnitude or non-existent. Few clues are available on this tumour variant. It is somewhat predominant in women, in subjects of blood group A phenotype, and less frequent in older subjects. Cell lines derived from diffuse carcinomas lack functional calcium dependent adhesion molecules ("cadherins"). Recent increases in incidence rates have been registered for adenocarcinoma of the gastric cardia. This increase parallels that of lower oesophageal adenocarcinoma, frequently linked with Barrett's oesophagus, reflux oesophagitis, a history of duodenal ulcer and gastric hypersecretion. New developments in molecular biology are being used to study the process of gastric carcinogenesis. There is hope that specific molecular alterations may provide better understanding of the different variants of gastric carcinoma and their secular trends.