Person: Bretthauer, Michael
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Bretthauer
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Michael
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Bretthauer, Michael
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Publication Bounding the per-protocol effect in randomized trials: an application to colorectal cancer screening(BioMed Central, 2015) Swanson, Sonja; Holme, Øyvind; Løberg, Magnus; Kalager, Mette; Bretthauer, Michael; Hoff, Geir; Aas, Eline; Hernan, MiguelBackground: The per-protocol effect is the effect that would have been observed in a randomized trial had everybody followed the protocol. Though obtaining a valid point estimate for the per-protocol effect requires assumptions that are unverifiable and often implausible, lower and upper bounds for the per-protocol effect may be estimated under more plausible assumptions. Strategies for obtaining bounds, known as “partial identification” methods, are especially promising in randomized trials. Results: We estimated bounds for the per-protocol effect of colorectal cancer screening in the Norwegian Colorectal Cancer Prevention trial, a randomized trial of one-time sigmoidoscopy screening in 98,792 men and women aged 50–64 years. The screening was not available to the control arm, while approximately two thirds of individuals in the treatment arm attended the screening. Study outcomes included colorectal cancer incidence and mortality over 10 years of follow-up. Without any assumptions, the data alone provide little information about the size of the effect. Under the assumption that randomization had no effect on the outcome except through screening, a point estimate for the risk under no screening and bounds for the risk under screening are achievable. Thus, the 10-year risk difference for colorectal cancer was estimated to be at least −0.6 % but less than 37.0 %. Bounds for the risk difference for colorectal cancer mortality (–0.2 to 37.4 %) and all-cause mortality (–5.1 to 32.6 %) had similar widths. These bounds appear helpful in quantifying the maximum possible effectiveness, but cannot rule out harm. By making further assumptions about the effect in the subpopulation who would not attend screening regardless of their randomization arm, narrower bounds can be achieved. Conclusions: Bounding the per-protocol effect under several sets of assumptions illuminates our reliance on unverifiable assumptions, highlights the range of effect sizes we are most confident in, and can sometimes demonstrate whether to expect certain subpopulations to receive more benefit or harm than others. Trial registration Clinicaltrials.gov identifier NCT00119912 (registered 6 July 2005) Electronic supplementary material The online version of this article (doi:10.1186/s13063-015-1056-8) contains supplementary material, which is available to authorized users.Publication Benefits and harms of mammography screening(BioMed Central, 2015) Løberg, Magnus; Lousdal, Mette Lise; Bretthauer, Michael; Kalager, MetteMammography 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.Publication Cecum intubation rate as quality indicator in clinical versus screening colonoscopy(© Georg Thieme Verlag KG, 2017) Hoff, Geir; Holme, Øyvind; Bretthauer, Michael; Sandvei, Per; Darre-Næss, Ole; Stallemo, Asbjørn; Wiig, Håvard; Høie, Ole; Noraberg, Geir; Moritz, Volker; de Lange, ThomasBackground and study aims Some guidelines recommend a minimum standard of 90 % cecal intubation rate (CIR) in routine clinics and 95 % in screening colonoscopy, while others have not made this distinction – both with limited evidence to support either view. This study questions the rationale for making such differentiation. Patients and methods We assessed cecum intubation rates amongst colonoscopies recorded in the Norwegian national quality register Gastronet by 35 endoscopists performing both clinical and screening colonoscopies. Colonoscopies were categorized into primary screening colonoscopy, work-up colonoscopy of screen-positives and clinical colonoscopy or surveillance. Cases with insufficient bowel preparation or mechanical obstruction were excluded. Endoscopists were categorized into “junior” and “senior” endoscopists depending on training and experience. Univariable and multivariable logistic regression analyses were applied. Results During a 2-year period, 10,267 colonoscopies were included (primary screening colonoscopy: 746; work-up colonoscopy of screen-positives: 2,604; clinical colonoscopy or surveillance: 6917). The crude CIR in clinical routine colonoscopy, primary screening colonoscopy and work-up colonoscopy was 97.1 %, 97.1 % and 98.6 %, respectively. In a multiple logistic regression analysis, there were no differences in CIR between the 3 groups. Poor bowel cleansing and female sex were independent predictors for intubation failure. Conclusion Cecal intubation rate in clinical colonoscopies and colonoscopy screening are similar. There is no reason to differentiate between screening and clinical colonoscopy with regard to CIR.Publication Prognosis in Women with Interval Breast Cancer: Population Based Observational Cohort Study(BMJ Publishing Group Ltd., 2012) Kalager, Mette; Tamimi, Rulla; Bretthauer, Michael; Adami, Hans-OlovObjective: To compare the prognosis in women with interval breast cancer (cancer detected after a normal screening mammogram and before the next scheduled mammogram) with breast cancer detected among women not yet invited to mammography screening (non-screened). Design: Population based observational study. Setting: Norwegian breast cancer screening programme, implemented in different counties from 1996 to 2005. Participants: 7116 women with a diagnosis of breast cancer at age 50 to 72 years; 1816 had interval breast cancer and 5300 had a diagnosis of breast cancer but had not yet been invited to screening. Main outcome measures: Characteristics of the breast tumours, and survival of the women using Kaplan Meier curves and multivariable Cox proportional hazard models. Results: Although interval cancers on average were slightly larger than the cancers in women not invited to screening, the histological type or status of axilliary lymph nodes did not differ noticeably between the two groups. Among interval cancers, there were no appreciable trends in size, nodal status, grade, or hormone receptor positivity associated with time since the last normal mammogram as a marker of growth rate. After 10 years of follow-up, the survival rates were 79.1% (95% confidence interval 75.4% to 82.3%) among women with interval cancers and 76.8% (75.3% to 78.2%) among women in the non-screened cancer group (hazard ratio 0.98, 95% confidence interval 0.84 to 1.15; P=0.53). Analyses stratified by time since last normal mammogram, age at diagnosis, or screening round showed similar results. Conclusion: The prognosis of women with interval breast cancers was the same as that of women with breast cancers diagnosed without mammography screening.Publication Improved Breast Cancer Survival Following Introduction of an Organized Mammography Screening Program among Both Screened and Unscreened Women: A Population-Based Cohort Study(BioMed Central, 2009) Kalager, Mette; Haldorsen, Tor; Bretthauer, Michael; Hoff, Geir; Thoresen, Steinar O; Adami, Hans-OlovIntroduction: Mammography screening reduces breast cancer mortality through earlier diagnosis but may convey further benefit if screening is associated with optimized treatment through multidisciplinary medical care. In Norway, a national mammography screening program was introduced among women aged 50 to 69 years during 1995/6 to 2004. Also during this time, multidisciplinary breast cancer care units were implemented. Methods: We constructed three cohorts of breast cancer patients: 1) the pre-program group comprising women diagnosed and treated before mammography screening began in their county of residence, 2) the post-program group comprising women diagnosed and treated through multidisciplinary breast cancer care units in their county but before they had been invited to mammography screening; and 3) the screening group comprising women diagnosed and treated after invitation to screening. We calculated Kaplan-Meier plots and multivariable Cox proportional hazard models. Results: We studied 41,833 women with breast cancer. The nine-year breast cancer-specific survival rate was 0.66 (95%CI: 0.65 to 0.67) in the pre-program group; 0.72 (95%CI: 0.70 to 0.74) in the post-program group; and 0.84 (95%CI: 0.80 to 0.88) in the screening group. In multivariable analyses, the risk of death from breast cancer was 14% lower in the post-program group than in the pre-program group (hazard ratio 0.86; (95%CI: 0.78 to 0.95, P = 0.003)). Conclusions: After nine years follow-up, at least 33% of the improved survival is attributable to improved breast cancer management through multidisciplinary medical care.