In medical research, statistical methods have been widely utilized. With enhanced expectations for real-world data, highly sophisticated statistical methods have recently been successfully introduced in practice. However, inappropriate application of statistical methods may be observed. Therefore, statistical thinking and reasoning should be appropriately shared among clinical researchers. In this study, we provide an introductory explanation of the statistics. Contrasting a recent randomized clinical trial and a recent observational study evaluating the effectiveness of endoscopies, fundamental ideas is introduced behind statistical methods widely used in clinical research. This is the second part in a series of two successive lectures.

Background: During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, attention should be paid to the risk of droplet infection during upper gastrointestinal endoscopy, because patients often cough or vomit during the test. We invented a non-woven fabric method in which the patient's mouth was covered during the upper endoscopic procedure. The purpose of this study was to confirm the tolerability of examinees using the non-woven fabric method and to clarify the cost.

Subjects and methods: In September 2020, we conducted a questionnaire survey of those who underwent upper gastrointestinal endoscopy at JCHO Shiga Hospital regarding their impressions of undergoing upper endoscopy with the non-woven fabric method. The cost of this method was also calculated.

Results: The questionnaire was administered to 307 examinees, and effective answers were returned by 293 persons (male/female: 185/108, mean age+-SD: 55.7+-11.6 y. o., return rate 95.4%). The proportion of examinees who complained of discomfort, dyspnea, oppression/closed sensation, and communication disturbance was 3.6%, 4.2%, 3.9%, and 2.0%, respectively. The cost of the method was approximately 2.8 yen per test.

Conclusion: The non-woven fabric method was acceptable to the patients undergoing upper GI endoscopy during the SARS-CoV-pandemic era, and the cost of these methods was low.

Objective: To improve gastric cancer mortality in Yamagata Prefecture, we investigated current community and occupational gastric cancer screening systems including accuracy controls.

Subject and Methods: We assessed improvement of screening systems and accuracy controls between fiscal years 2016 and 2018 at prefecture, municipal, and screening center levels using a previously developed gastric cancer-screening evaluation check list.We also assessed screening process indices from 207,341 individuals who underwent gastric cancer screenings in the fiscal year 2018. We further compared the number of gastric cancer deaths with cancer screening participation rate by age group.

Results: While the accuracy controls of prefecture and municipal screenings were improved, those of screening centers remained the same. Although all screening process indices from community screenings were higher than acceptable values, those of workplace screenings remained low, and when community and workplace screenings were combined, the diagnostic screening rate was particularly low. It is noted that the screening participation rate of individuals aged 75 years and older was low despite a higher number of cancer deaths and mortality within this age group.

Conclusions: Results suggest that improvement in the diagnostic screening rate at workplace screenings is required and that promotion of community screening for individuals aged 75 years and older may improve gastric cancer mortality in Yamagata Prefecture.

The patient, a man in his 60s, had a history of drinking 500 mL of shouchu each day for 44 years. He also had a history of smoking 40 cigarettes a day for 30 years, but had quit at the age of 50. He underwent gastroendoscopy every year, but no abnormalities were observed in his pharynx. When gastroendoscopy at 200X was performed, tumor lesions were observed in the left wall of the hypopharynx for the first time. Retrospectively, endoscopic images obtained 1 year ago showed no obvious lesions. As a result of the biopsy, he was diagnosed with pharyngeal squamous cell cancer. Then, he visited the Otorhinolaryngology Department of Miyazaki Prefectural Miyazaki Hospital and underwent chemoradiotherapy treatment with diagnosis of T2N0M0 and Stage II. The patient is well and alive six and a half years later. The fact that the medical examination endoscopy was performed every year with transnasal endoscopy appears to be a contributing factor to his survival. In addition, the examination interval for population-based gastroscopic screening was every 2 years, and the lesion was beyond the scope of population-based screening. In not only this case, but also in esophageal, oral, and pharyngeal cancer, which have worse prognosis than gastric cancer, (especially in men with hypopharyngeal cancer), it is necessary to consider that patients with contributing risk factors such as alcohol consumption and smoking, and men should be examined by opportunistic screening or insurance treatment outside of the biennial population-based screening time frame.

A man in his 70s underwent endoscopic examination for gastric cancer as part of the 2019 Saitama City screening program. A 5-mm, bright crimson Yamada type III polyp was identified at the greater curvature of the gastric corpus, with no atrophy in the background mucosa. Raspberry-like foveolar-type gastric adenocarcinoma, which has been the subject of attention in recent years, was suspected, and biopsy was performed. Pathological testing of the biopsy sample revealed a mixture of foveolar hyperplastic and adenomatous components and the patient was referred to the Jichi Medical University Saitama Medical Center. Combined narrow-band imaging and magnified observations showed a papillary structure to the lesion, a thinned white zone, and a dilated interfoveolar area containing abnormally proliferating blood vessels with irregular courses. The lesion was removed en bloc by endoscopic submucosal dissection, and a low-grade, well-differentiated adenocarcinoma was diagnosed. No atrophy of the background gastric mucosa was observed. As tests for Helicobacter pylori immunoglobulin G antibodies were negative, the lesion was regarded as H. pylori-negative gastric cancer. Cases of foveolar-type gastric adenocarcinoma with a raspberry-like appearance have been reported in recent years, and may be overlooked during screening tests because of their close resemblance to ordinary foveolar hyperplastic polyps. When crimson polyp resembling ordinary hyperplastic polyp on H. pylori-negative gastric mucosa is identified, careful attention is required in screening tests to correctly diagnose the polyps.