2018 Volume 56 Issue 4 Pages 479-489
According to “Categorized Criteria for X-Ray Image Reading of the Population-Based Gastric Cancer Screening,” which has been published by the Japanese Society of Gastrointestinal Cancer Screening, the radiographic findings in the examinees who require close examination are classified into Category (C)-3a, C-3b, C-4, and C-5, depending on the probability of existence of a lesion and the strength of suspicion for malignancy. Of the 10365 examinees who required close examination among 181224 participants in the radiographic screening program in 2015 (rate of close examination required: 5.7%), the frequencies of C-3a, C-3b, C-4, and C-5 were 16.2%, 81.5%, 2.0%, and 0.4%, respectively. Thus, C-3b was most frequent category for which close examination was required. In total, 334 cases of gastric cancer were detected by screening in 2015 (detection rate: 0.18%). The positive predictive values (PPV) of C-3a, C-3b, C-4, and C-5 were 1.5%, 2.7%, 35.4%, and 71.8%, respectively. The PPV of the categorized criteria significantly increased from C-3a to C-5. The lesions of gastric cancer classified as C-3a, C-4, and C-5 were well-expressed in the X-ray images. Among them, the C-3a cases were mainly cases of intraepithelial cancer, but C-4 cases showed increased frequency of submucosal cancers, and the majority of C-5 cases were those of advanced cancers. The C-3b cases also comprised many intraepithelial or submucosal cancers, but most of them were pointed out by uncertain findings due to inadequate imaging or by findings unrelated to the lesions in the X-ray images. Thus, the categorized criteria are considered as useful indices for objective evaluation of the diagnostic process during X-ray image reading, but further discussion on its operation and usage is required.
