Expectations for and challenges in population-based endoscopic gastric and colorectal cancer screening.

Abstract

In 2019, 376,425 people died of cancer in Japan (220,339 men, 156,086 women). Lung cancer was the most common cause of cancer death (75,394 deaths), followed by colorectal (51,420 deaths) and gastric cancer (42,931 deaths).1 Gastric cancer ranked second for men and fourth for women, while colorectal cancer ranked third for men and first for women. To reduce gastric and colorectal cancer deaths, the national government must strengthen both primary and secondary prevention. Cancer screening in Japan can be divided into population-based screening, which aims to reduce overall mortality rates in target populations, and opportunistic screening, which aims to reduce individual risk. Robust population-based screening is a foundation of cancer control in Japan. In 2016, the Ministry of Health, Labour, and Welfare guidelines began recommending biennial gastroscopy for people aged ≥50 years during population-based screening. The fecal immunochemical test (FIT, two-day method) has been used in population-based colorectal cancer screening for people aged ≥40 years since 1992. Colonoscopy has not yet been introduced. In Japan, age-adjusted morbidity and mortality in people aged <75 years have shown clear downward annual trends for gastric cancer since the 1980s, but have not declined for colorectal cancer.1 However, age-adjusted mortality rates for colorectal cancer have shown clear downward trends in the United States (U.S.) and Britain. In the U.S., there are an estimated 150,000 colorectal cancer patients and 50,000 colorectal cancer deaths annually. The numbers are similar in Japan; however, the U.S. population is approximately 2.5 times larger than Japan's. Examining age-adjusted gastric and colorectal cancer mortality rates in people <75 years by prefecture shows gastric cancer rates are significantly higher on the Sea of Japan coast, while colorectal cancer rates are significantly higher in northern Kanto and in some Kyushu prefectures (Fig. 1). There was a weak positive correlation between age-adjusted gastric cancer mortality and colorectal cancer mortality (correlation coefficient 0.354). A strong positive correlation (correlation coefficient 0.883) was observed between gastric and colorectal cancer screening rates in each prefecture (Fig. 2). However, screening rate and age-adjusted mortality were not correlated for either gastric or colorectal cancer. The “Guidelines for gastric cancer screening based on efficacy evaluation” state: “Gastroscopy is recommended in population-based screening. Screening should be conducted on people aged 50 and older, with 2–3 years between screening. However, it should not be performed if there is no system capable of responding quickly and appropriately to serious complications.” In addition to establishing a system for monitoring accuracy, the advantages and disadvantages should be fully explained. In 2018, the National Cancer Center was commissioned by the Ministry of Health, Labour, and Welfare to request a survey on the status of cancer screening in municipalities.2 Of the 1735 municipalities that performed gastric cancer screening, 574 (33.1%) used gastroscopy in either mass or individual screening – an 8% increase from the 437 municipalities (25.3%) of the previous fiscal year. While this shows that gastroscopic examinations are gradually expanding nationwide, they are not yet sufficiently widespread. The following factors were cited as reasons why municipalities have not introduced gastroscopic screening: no vendors to perform gastroscopic screening and lack of necessary facilities or equipment, a system for monitoring accuracy, and funds. In an earlier survey by the Japan Gastroenterological Endoscopy Society (JGES), most municipal governments and medical associations cited issues regarding capacity in endoscopy frameworks and development of accuracy monitoring systems; many also cited a shortage of specialists. The JGES has 17,850 endoscopy specialists and 6205 instructors (as of February 2017), but they are over-concentrated in urban areas. Figure 3 shows the relationship between age-adjusted gastric cancer mortality rate in people under age 75 and the number of endoscopy specialists. The number of endoscopy specialists per population for people aged ≥40 years was highest in Ishikawa Prefecture, followed by Tokyo, Kyoto, Fukui, and Wakayama. While high age-adjusted mortality rates in Aomori, Iwate, Niigata, and Akita may suggest a shortage of specialists, no significant correlation was observed between age-adjusted mortality and number of endoscopy specialists (correlation coefficient −0.22). According to the Ministry of Health, Labour, and Welfare,3 >10 million upper gastrointestinal endoscopy examinations covered by health insurance are performed annually, including those performed for screening purposes. The Japan Endoscopy Database (JED) Project4, 5 aims to collect detailed data on patients who undergo gastroenterological endoscopy in Japan, the doctors and assistants who perform the examinations, the rate of lesion detection, complication incidence, and other factors. This will hopefully help to determine the optimal method of assigning specialists for gastroscopy screening, endoscopic examination frameworks, accuracy monitoring systems, and training systems. Guidelines for colorectal cancer screening based on efficacy evaluation were published in 2005.6 Total colonoscopy (TCS) and sigmoidoscopy were assigned a grade C recommendation: they can be used in opportunistic screening but are not recommended for population-based screening. Colorectal cancer mortality rates in the U.S. have been decreasing since the 1980s due to colorectal cancer control initiatives incorporating TCS. It may be difficult to apply U.S. methods to Japan due to differences in health insurance systems and other factors; however, Japan should consider introducing TCS during screening. Five randomized controlled trials assessing the effects of TCS in colorectal cancer screening on reducing mortality are currently in progress.7-11 The Akita pop-colon trial randomly assigned participants to an initial TCS intervention or a non-intervention group.8 Although the primary endpoint of this study is colorectal cancer death, it is expected to produce valuable findings regarding population-based TCS screening, including differences between groups in colorectal cancer stage, the incidence of complications, and clinicopathological features of the discovered lesions. Cancer screening effectiveness is evaluated by the ability to reduce mortality rates. When considering whether an examination method can be applied to cancer screening, basic research is required to determine its accuracy and detection power. Therefore, data from the Akita pop-colon trial,8 the Nii-jima/Oshima study,12 and the Japan Polyp Study cohort13 will likely be beneficial when revising guidelines. However, the following issues need to be resolved before population-based TCS screening can be implemented: ensuring TCS safety and quality; processing capacity; medical-economic assessments; adherence; and creating a TCS screening database.14 Figure 4 shows the relationship between age-adjusted colorectal cancer mortality rates in people aged <75 years and the number of endoscopy specialists. Unlike gastric cancer, a weak negative correlation was observed (correlation coefficient −0.33), suggesting that properly assigning endoscopy specialists may reduce colorectal cancer mortality. Ensuring safety, quality, and sufficient capacity will likely be more difficult in population-based TCS screening than gastroscopic screening and will thus be a major challenge to implementing population-based TCS screening. Regulation of doctors performing the examination is also needed. The Markov model suggested aggressive TCS use for screening in Japan would have excellent cost-effectiveness from the outset.15 However, concerns regarding adherence and increasing TCS examinations exist. TCS should be used more actively in screening according to its capacity; therefore, it may be worth considering a screening method based on FIT but that performs TCS on people of a certain age. Colorectal cancer mortality in Japan would inevitably decrease if all citizens in their 50s underwent a single TCS screening. If all of the approximately 18 million people in Japan in their 50s were given a free on-time TCS in their lifetime and if 5% were screened annually, a capacity of 900,000 TCS screenings/year would be required. Considering health check recommendations set by municipal governments, ease of data management, and limitations on the number of TCS screenings that can be performed, the most practical method would be to provide TCS screening to certain ages (i.e. at 55 and 65 years old) and FIT to everyone else. There are high hopes the JED Project can play a similar role in creating a TCS screening database as it has for gastroscopic screening. To evaluate the effects of screening on reducing mortality rates, screening data must be managed at a high degree of accuracy at the level of municipal residence certificates. Therefore, a system able to link this database to cancer registration data and JED data will need to be built. This article outlined the possibilities of and challenges facing gastric and colorectal endoscopic screening regarding recent trends in gastric and colorectal cancer in Japan. Population-based gastroscopic screening is a national policy; however, it has been introduced in only 33% of the 1735 municipalities that conduct gastric cancer screening due to lack of capacity in endoscopy frameworks and insufficient accuracy monitoring systems. Aggressive action aimed at introducing population-based colonoscopy screenings is needed, while ensuring TCS safety, quality, and sufficient capacity. JGES's soon-to-launch system for certifying physicians in endoscopic screening hopes to be a driving force behind this. Japan has long been a world leader in endoscopic diagnosis and treatment techniques. It is hoped that the 100th anniversary of JGES will be a turning point on the path to lower mortality rates for gastric and colorectal cancers in Japan by increasing availability of safe and high-quality population-based gastroscopic screening and introducing colonoscopy examinations to population-based screening. I would like to thank my colleagues Dr Masau Sekiguchi, Dr Yasuo Kakugawa, Dr Keiko Nakamura, and Dr Yutaka Saito, for their valuable advice regarding the contents of this manuscript. Author T.M. IS an Associate Editor of Digestive Endoscopy. This manuscript was supported by the National Cancer Center Research and Development Fund (2021-A-18).