Abstract
In Japan, gastric cancer screening using double-contrast barium X-ray examinations is performed throughout the country as a public health service, and it has greatly contributed to the reduction in cancer mortality rates. Although the nationwide gastric cancer screening programs have been an unparalleled success, the current gastric cancer screening program is now facing many problems, including a decreasing screening rate and its low sensitivity in comparison with endoscopy. Meanwhile, it has become clear that Helicobacter pylori is the major risk factor for gastric cancer, and that the gastritis-atrophy-metaplasia-cancer sequence triggered and driven by H. pylori infection is the main-route of this cancer's development. These facts have gradually led to a shift in the anti-gastric cancer strategy in Japan from secondary prevention by cancer screening to primary prevention by H. pylori eradication. In addition, long-term observational studies have demonstrated that the stage of the gastritis-atrophy-metaplasia-cancer sequence induced by H. pylori infection together with the associated cancer risk in each individual can be roughly estimated non-invasively based on two serum tests, pepsinogen (PG) and the H. pylori-specific antibody titer. Theoretically, this is an innovative method not only for identifying groups that would benefit from gastric cancer prevention measures such as screening, but also for improving the efficiency of such measures by excluding low-risk groups. Nevertheless, major issues remain, such as the difficulty in the serologic diagnosis of subjects with low cancer risk due to the low sensitivity of the presently available serologic tests for the H. pylori-specific antibody titer or the incomplete exclusion of subjects with extensive atrophy according to the PG test-positive criteria widely used in Japan. In addition, assessment of the risk for undifferentiated cancer, which is considered to develop via a de novo pathway, is incomplete, and constitutes another problem warranting investigation. Full and careful consideration is urgently required before introducing this method for actual cancer screening in Japan.
