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In this randomized trial involving 84,585 participants in Poland, Norway, and Sweden, the risk of colorectal cancer at 10 years was lower among those invited to undergo screening colonoscopy than among those assigned to no screening.

Evaluating diagnostic tests in learning screening programs could improve public health National cancer screening programs, such as mammography for breast cancer, are widely implemented to reduce cancer incidence and mortality in high-income countries. Their introduction is also being considered in low- and middle-income countries. For many cancer types, the benefits and harms of different screening tests and the intervals at which they should be implemented are unknown. Thus, randomized comparison testing is warranted. However, this is not possible because most people in high-income countries have already undergone screening or have refused screening and are not comparable ( 1 ). There is an ethical, medical, economic, and societal imperative for continuous evaluation of cancer screening programs to ensure that their benefits outweigh any harms. This may be achievable if the screening programs can become the arena for clinical testing through the implementation of learning screening programs.

Mammography screening for breast cancer is widely available in many countries. Initially praised as a universal achievement to improve women's health and to reduce the burden of breast cancer, the benefits and harms of mammography screening have been debated heatedly in the past years. This review discusses the benefits and harms of mammography screening in light of findings from randomized trials and from more recent observational studies performed in the era of modern diagnostics and treatment. The main benefit of mammography screening is reduction of breast-cancer related death. Relative reductions vary from about 15 to 25% in randomized trials to more recent estimates of 13 to 17% in meta-analyses of observational studies. Using UK population data of 2007, for 1,000 women invited to biennial mammography screening for 20 years from age 50, 2 to 3 women are prevented from dying of breast cancer. All-cause mortality is unchanged. Overdiagnosis of breast cancer is the main harm of mammography screening. Based on recent estimates from the United States, the relative amount of overdiagnosis (including ductal carcinoma in situ and invasive cancer) is 31%. This results in 15 women overdiagnosed for every 1,000 women invited to biennial mammography screening for 20 years from age 50. Women should be unpassionately informed about the benefits and harms of mammography screening using absolute effect sizes in a comprehensible fashion. In an era of limited health care resources, screening services need to be scrutinized and compared with each other with regard to effectiveness, cost-effectiveness and harms.

This analysis of Norwegian registry data suggests that colonoscopic surveillance during the 8 years after removal of low-risk adenomas is not required for a reduction in colorectal-cancer mortality. Screening programs for colorectal cancer are currently implemented in many Western populations 1 , 2 because randomized trials have documented an association between screening and a sustained reduction in colorectal-cancer mortality. 3 The benefit is most likely due to early detection of cancer, endoscopic removal of adenomas, and surveillance of patients who are considered to be at high risk for the development of new neoplastic lesions. 4 , 5 However, precise quantification of the risk of death from cancer after adenoma removal has been hampered by the scarceness of large, population-based studies with long follow-up periods. Previous studies were performed in populations undergoing intensive surveillance, . . .

Background Norway and Sweden have similar populations and health care systems, but different reactions to the COVID-19 pandemic. Norway closed educational institutions, and banned sports and cultural activities; Sweden kept most institutions and training facilities open. We aimed to compare peoples’ attitudes towards authorities and control measures, and perceived impact of the pandemic and implemented control measures on life in Norway and Sweden. Methods Anonymous web-based surveys for individuals age 15 or older distributed through Facebook using the snowball method, in Norway and Sweden from mid-March to mid-April, 2020. The survey contained questions about perceived threat of the pandemic, views on infection control measures, and impact on daily life. We performed descriptive analyses of the responses and compared the two countries. Results 3508 individuals participated in the survey (Norway 3000; Sweden 508). 79% were women, the majority were 30–49 years (Norway 60%; Sweden 47%), and about 45% of the participants in both countries had more than 4 years of higher education. Participants had high trust in the health services, but differed in the degree of trust in their government (High trust in Norway 17%; Sweden 37%). More Norwegians than Swedes agreed that school closure was a good measure (Norway 66%; Sweden 18%), that countries with open schools were irresponsible (Norway 65%; Sweden 23%), and that the threat from repercussions of the mitigation measures were large or very large (Norway 71%; Sweden 56%). Both countries had a high compliance with infection preventive measures (> 98%). Many lived a more sedentary life (Norway 69%; Sweden 50%) and ate more (Norway 44%; Sweden 33%) during the pandemic. Conclusion Sweden had more trust in the authorities, while Norwegians reported a more negative lifestyle during the pandemic. The level of trust in the health care system and self-reported compliance with preventive measures was high in both countries despite the differences in infection control measures.

Many methods are available for colorectal cancer (CRC) screening, ranging from noninvasive stool tests to endoscopy. In this Review, E. J. Kuipers et al . argue that the strength of any single test must be viewed in the context of a range of factors across the screening programme, including test characteristics, uptake, screenee autonomy, cost, endoscopy performance and long-term follow-up. The first evidence that screening for colorectal cancer (CRC) could effectively reduce mortality dates back 20 years. However, actual population screening has, in many countries, halted at the level of individual testing and discussions on differences between screening tests. With a wealth of new evidence from various community-based studies looking at test uptake, screening-programme organization and the importance of quality assurance, population screening for CRC is now moving into a new realm, promising better results in terms of reducing CRC-specific morbidity and mortality. Such a shift in the paradigm requires a change from opportunistic, individual testing towards organized population screening with comprehensive monitoring and full-programme quality assurance. To achieve this, a combination of factors—including test characteristics, uptake, screenee autonomy, costs and capacity—must be considered. Thus, evidence from randomized trials comparing different tests must be supplemented by studies of acceptance and uptake to obtain the full picture of the effectiveness (in terms of morbidity, mortality and cost) the different strategies have. In this Review, we discuss a range of screening modalities and describe the factors to be considered to achieve a truly effective population CRC screening programme. Key Points Screening is a very cost-effective method for reducing colorectal cancer (CRC) incidence and mortality and includes noninvasive faecal occult blood tests and faecal immunochemical tests as well as sigmoidoscopy and colonoscopy Opportunistic, individual testing is now shifting towards organized population screening with monitoring and full-programme quality assurance As such, the focus shifts from the test alone to factors across the screening programme in combination, including test characteristics, uptake, screenee autonomy, cost, endoscopy performance and long-term follow-up Targeting each of these factors will increase population coverage, improve overall quality and decrease quality variation, which will improve the preventive effect of screening and markedly reduce CRC incidence and mortality

In this correspondence we respond to critique of our randomized trial of Covid-19 transmission in fitness centers. The trial was performed in Norway during May and June 2020. Keywords: Covid-19, Randomized trial, Public health