Epidemiological studies on cancer screening can be mainly classified into two areas: assessment on whether cancer screening is effective and management which confirms whether cancer screening is conducted correctly. Epidemiological studies have proven the scientific evidence of both areas in cancer screening. Their quality depends on how chance, bias, and confounding are controlled. Chance and bias can be controlled in the study design, whereas confounding factors are controlled in both the study design and analysis.

Cancer screening efficacy should be evaluated by the reduction of cancer mortality, rather than improvement of survival, since the latter is affected by several biases. Randomized controlled trials with individual-based allocation can control chance, bias, and confounding at the best level, while case-control and cohort studies are used as observational studies. Although overdiagnosis is recognized as an important disadvantage of cancer screening, quantitative evaluation methods are still being discussed. For the management of cancer screening, the attendance rate for further diagnostic tests, screening positive rates, and cancer detection rates are currently used. It is expected that the sensitivity, specificity, and cancer prevalence rate will be used as alternative more effective indicators in future cancer screening.

The detectability of colorectal tumors of 10 mm or more has the same accuracy in computed tomographic (CT) colonography as in colonoscopy. In addition, CT colonography is minimally invasive and safe, can be standardized from the objectivity and reproducibility of images, and a large number of patients can be examined in a short time, making it a suitable screening method for colorectal cancer. CT colonography is expected to be a detailed test for patients with positive fecal immunochemical tests; however, issues, such as variability of bowel preparation and availability of radiologists, need to be considered. Colonoscopy is the most sensitive and specific screening method, and its introduction into colorectal cancer screening can be expected to contribute greatly to the reduction of mortality. However, colonoscopy has several drawbacks, such as the need to ensure safety and quality, colonoscopy capacity, surveillance period, cost effectiveness, and accuracy.

In order to reduce colorectal cancer mortality in Japan, it is important to provide efficient diagnostic imaging interventions in the colorectal cancer screening system, which has been conducted principally using the fecal immunochemical test, and to construct a more effective and systematic screening system. In addition, it is important to thoroughly manage the accuracy of each test with the aim of further improving the screening rates and the rate of undergoing close examination after a positive fecal immunochemical test.

Objective: We investigated the utility of thermometry, inquiry, and COVID-19 antigen test before screening esophagogastroduodenoscopy (EGD) in medical examination during the COVID-19 pandemic.

Subjects and methods: Thermometry, inquiry, and COVID-19 antigen testing were performed before EGD for 119 medical examinees between July 20, 2020 and August 5, 2020. Staff members working in the endoscopic unit wore appropriate personal protective equipment (PPE) while working and undertook reverse-transcription PCR (RT-PCR) just after the survey period.

Results: One examinee had a fever over 37°C (37.1°C), while five had slight symptoms of common cold. COVID-19 antigen tests were negative for 115 cases, including six cases in which examinees had slight symptoms, whereas four examinees judged as quasi-positive were confirmed to be COVID-19-negative by RT-PCR.

All examinees underwent EGD, and two examinees were diagnosed with early gastric cancer. Immediately after the survey period, all 29 staff members working in the endoscopic unit were confirmed to be COVID-19-negative by RT-PCR.

Conclusions: This approach can efficiently rule out a large percentage of COVID-19 patients, and screening EGD in medical examination should be continued and accompanied with thorough infection prevention including PPE and education.

Background: Bowel preparation plays an important role in performing colonoscopy. However, it may lead to complications in some cases. Therefore, its current status should be clearly understood for formulating a more reliable and safer procedure.

Subjects and methods: An internet questionnaire survey was conducted among medical doctors, nurses, and technicians regarding preparation methods for performing colonoscopy in their respective institutions and their awareness of colonoscopy preparation.

Results: A total of 200 medical doctors, 70 nurses, and 60 technicians who met the eligibility criteria were recruited. All medical doctors and approximately 90% of the nurses and technicians understood the risk of using a lavage solution. Patient information was interviewed almost 100% by either occupation. According to the patient information provided during the interview, stenosis was suspected in the distal colon in one case, and bowel movements were not observed after taking a laxative or lavage solution in another case; almost all occupations took appropriate action according to each situation. However, answer to the question of whether a corresponding manual according to the situation is already prepared varied among occupations. In particular, 40% of medical doctors and 20% of nurses and technicians answered that they have no corresponding manual for patients who were taking lavage solution at home. Therefore, urgent action is required to prevent complications in these patients.

Conclusions: All healthcare professionals should be trained for possible complications by reaffirming the risks of bowel preparation and sharing patient information.

Objective: In colonography computed tomography (CTC), it is important to accurately evaluate the polyp size using CT colonography reporting and data system (C-RADS). This study aims to determine the proper window width (WW) and the exposure dose to obtain accurate polyp size.

Subjects and methods: Each of 5 mm, 7 mm, and 10 mm of the CTC phantom polyps were scanned by the exposure dose standard deviation (SD) 8 and SD 30. The WW was changed by 300, 600, 900, 1,200, 1,500, and each 10 blinded radiologists measured all data. A proper WW is defined if the polyp measurement is within±5 % of the actual size.

Results: The measured polyp size values increase with increased WW. SD 30 exhibited a more variant polyp size than that of SD 8. The diameter of the polyp was more variant than its height. Accurate WW at 5 mm polyp was 600-1,500, at 7 mm was 600-1,000, and 10 mm was 800-1,000. Therefore, the WW that satisfied all was 800-1,000.

Conclusion: The measurement of polyp size should use WW of 800-1,000 in using C-RADS.