[in Japanese]

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We investigated the efficiency of mass screening for stomach cancer using barium X-ray method in combination with serum pepsinogen (PG) test method. We performed the mass screening using both the X-ray and PG test methods simultaneously on 4,359 subjects over a period of 3 years, from 2000 to 2002. Serum PG I concentration of less than 50 ng/ml and a ratio of PG I to PG II of less than 3.0 were adopted as the criteria for positive result in our serum PG test method. The rate of individuals who needed further examination using endoscopy was 11.0% in X-ray method, 17.1% in serum PG test method, and 24.9% in both methods, respectively. Seven cases of stomach cancer were detected in the screening. The detection rate of stomach cancer in the screening was 0.16%. Three out of seven stomach cancer cases were detected among the subjects with positive serum PG test. All of these three cases were early stomach cancer and were not detected by X-ray method. Three other cases of stomach cancer, comprising one early and two advanced diseases, were detected among the subjects who required further examination in X-ray method. In all of these three cases serum PG test was negative. Only one early stomach cancer was detected among the subjects who required further examination in both methods. When serum PG I concentration of less than 30ng/ml and a ratio of PG I to PG II of less than 2.0 were adopted as the criteria for positive result in serum PG test method, the rate of individuals who needed further examination was decreased to 17.1% and the cancer detection rate was 0.14%, which was comparable to that in our screening method. This study indicates that serum PG I concentration of less than 30ng/ml and a ratio of PG I to PG II of less than 2.0 should be adopted as the criteria of positive result for the efficient mass screening using barium X-ray method in combination with serum PG test. Based upon the cost-benefit analysis in this study, we consider that annual barium X-ray method in combination with serum PG test on every-5-year basis or barium X-ray method alternated annually with serum PG test method is more useful for efficient mass screening for stomach cancer.

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The results of mass screening for gastric cancer in the employee using endoscopy from 1993 to 2003 fiscal year were examined. The endoscopic examinations were performed in 50, 276 cases. On these occasions, 77 gastric cancer cases were detected. By means of the accurate follow-up study, it became clear that the false negative rate of gastric cancer within three years after the initial examinations from 1993 to 2000 fiscal year amounted to 38.1%. The false negative cases are not always caused by the overlooks, but also by the inevitable reasons. But it is necessary that endoscopists do their best in order to reduce the false negative rate. In conclusion, though the endoscopic examinations were regarded as “gold standard” in mass screening for gastric cancer, endoscopists should always mind that the false negative cases can occur and should therefore examine endosopy as careful and exact as possible.

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Although there is sufficient evidence to suggest that colorectal cancer screening is effective in reducing the mortality from colorectal cancer, interval cancers discovered in fecal occult bloodnegative individuals through examinations other than the screening are a problem. In order to clarify the situation of interval cancer, examinees of checkups conducted in 1992-1995 (144, 295 subjects; ratio of subjects who required thorough examination: 5.1%; ratio of subjects who underwent thorough examination: 74.0%) underwent cancer registration and were followed up for 2 years. Of the 203 patients in which invasive cancer was discovered, 98 cases were true positive and 25 were false negative on thorough examination; 19 did not undergo thorough examination; 33 were false negative for occult blood and were found at annual or biennial screenings; 28 patients had interval cancer, accounting for 14%. The interval cancer was located in the right colon in 14 of the 28 patients, and this was more frequent than in the other 4 groups (P=0.089). The degree of differentiation of the cancer was poor in 4 of the 28 patients, but this frequency is significantly higher than that in the other groups (P<0.001). The cumulative 5-year survival rate was 63.9% in cases of interval cancer, significantly lower than those in the other groups: 96.7% in the cases which were false negative for occult blood and which were found in annual or biennial screenings and 82.0% in the true positive group. But it is noteworthy that the cumulative survival rate for interval cancer is equal to that of the cancers discovered in people who were not screened.

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The recent degradation of radiologists' ability to read the gastric X-ray film and the shortage of doctors who engage in screening are nation-wide problems in Japan. In the radiology department of Kumamoto University, radiologists who have been screening for over 5 years take turns in reading the gastric X-ray film. Then the films are double checked by the radiologists who have more than 10 years of experience. And case study conferences are held regularly for radiologists to develop their faculties. We have tested 8 radiologists who have different numbers of years of experience, in order to evaluate the present system of and the training method for gastric X-ray reading. The result was that the longer the experience, the better the grades. The result also suggested that even 10 years of experience is not enough to achieve sufficient mastery. Because there are not many opportunities to examine gastric X-ray images daily, it is very difficult for radiologists to develop their reading ability. We cannot say that the present training for the reading of gastric X-ray films at Kumamoto University has not had any effects on the results of the screening. It is our urgent task to improve the reading ability of our radiologists, and to develop a training system which can consolidate their reading abilities efficiently.

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