BACKGROUND We estimated breast cancer (BC) mortality reduction associated with invitations to a nation-wide population based screening program and changes in treatment, in Norway. MATERIAL AND METHODS BreastScreen Norway started in 1996 and became nationwide in 2005. It invites women aged 50-69 to biennial mammographic screening. We retrieved individual-level data for 1,340,333 women from national registries. During 1996-2014 (screening window), women contributed person-years (PY) in non-invited and invited periods. We created comparable periods for 1977-1995 (pre-screening window) by dividing the follow-up time for each woman into a pseudo-non-invited and pseudo-invited periods. We estimated BC mortality for the four periods, using the so-called evaluation model: counting BC deaths in each period for all women diagnosed within the period, counting BC deaths and person-years after screening-age only for women diagnosed within screening-age. We used a multivariable flexible parametric survival model to estimate hazard ratio (HR) for the effect of invitation and improved treatment. RESULTS There were 5818 BC deaths across 16,533,281 PY. Invitations to screening reduced BC mortality by 20% (HR: 0.80, 95%CI: 0.70-0.91) among women ≥50 years old and by 25% (HR: 0.75, 95%CI: 0.65-0.86) among screening-aged women. The treatment effect was 23% (HR: 0.77, 95%CI: 0.65-0.92) for women ≥50 years old, and 17% (HR: 0.83, 95%CI: 0.74-0.94) for screening-aged women. CONCLUSION We observed a similar reduction in BC mortality associated with invitations to screening and improvements in treatment among women ≥50 years old, during 1977-2014.

中文翻译：

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在挪威实施有组织的基于人群的乳腺癌筛查后的乳腺癌死亡率。

背景技术我们估计，在挪威，与邀请参加基于全国人群的筛查计划和治疗方法改变相关的乳腺癌（BC）死亡率降低。材料和方法BreastScreen Norway于1996年成立，并于2005年在全国范围内进行。该计划邀请50-69岁的女性进行两年一次的乳房X线检查。我们从国家注册处检索了1,340,333名女性的个人数据。在1996-2014年期间（筛选窗口），妇女在非邀请和邀请期间贡献了人年（PY）。我们通过将每个女性的随访时间分为伪非邀请期和伪邀请期，来创建1977-1995年的可比较时期（预筛查期）。我们使用所谓的评估模型估算了四个时期的BC死亡率：计算该时期内诊断出的所有女性在每个时期的BC死亡人数，仅针对在筛查年龄范围内诊断出的女性计算筛查年龄后的BC死亡人数和人年。我们使用了多变量灵活的参数生存模型来估计危险比（HR）的诱因和改善的治疗效果。结果公元前16,533,281年有5818 BC死亡。接受筛查的邀请使≥50岁的女性的BC死亡率降低了20％（HR：0.80，95％CI：0.70-0.91），而筛查年龄的女性降低了25％（HR：0.75，95％CI：0.65-0.86） 。≥50岁的女性的治疗效果为23％（HR：0.77，95％CI：0.65-0.92），筛查年龄的女性为17％（HR：0.83，95％CI：0.74-0.94）。结论我们观察到1977-2014年间，≥50岁的女性接受筛查和治疗改善相关的BC死亡率有类似的降低。