Harvard School of Public Health, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Ann Intern Med. 2012 Apr 3;156(7):491-9. doi: 10.7326/0003-4819-156-7-201204030-00005.
Precise quantification of overdiagnosis of breast cancer (defined as the percentage of cases of cancer that would not have become clinically apparent in a woman's lifetime without screening) due to mammography screening has been hampered by lack of valid comparison groups that identify incidence trends attributable to screening versus those due to temporal trends in incidence.
To estimate the percentage of overdiagnosis of breast cancer attributable to mammography screening.
Comparison of invasive breast cancer incidence with and without screening.
A nationwide mammography screening program in Norway (inviting women aged 50 to 69 years), gradually implemented from 1996 to 2005.
The Norwegian female population.
Concomitant incidence of invasive breast cancer from 1996 to 2005 in counties where the screening program was implemented compared with that in counties where the program was not yet implemented. To adjust for changes in temporal trends in breast cancer incidence, incidence rates during the preceding decade were also examined. The percentage of overdiagnosis was calculated by accounting for the expected decrease in incidence following cessation of screening after age 69 years (approach 1) and by comparing incidence in the current screening group with incidence among women 2 and 5 years older in the historical screening groups, accounting for average lead time (approach 2).
A total of 39,888 patients with invasive breast cancer were included, 7793 of whom were diagnosed after the screening program started. The estimated rate of overdiagnosis attributable to the program was 18% to 25% (P < 0.001) for approach 1 and 15% to 20% (P < 0.001) for approach 2. Thus, 15% to 25% of cases of cancer are overdiagnosed, translating to 6 to 10 women overdiagnosed for every 2500 women invited.
The study was registry-based.
Mammography screening entails a substantial amount of overdiagnosis.
Norwegian Research Council and Frontier Science.
由于缺乏有效的对照组来确定发病率趋势归因于筛查还是归因于发病率的时间趋势，因此一直难以精确量化乳腺癌（定义为如果没有乳房 X 光筛查，女性一生中就不会出现的癌症病例百分比）的过度诊断。
估计乳腺癌因乳房 X 光筛查而过度诊断的百分比。
比较有和无筛查的浸润性乳腺癌发病率。
挪威全国性的乳房 X 光筛查计划（邀请 50 至 69 岁的女性参加），从 1996 年到 2005 年逐渐实施。
挪威女性人群。
在实施筛查计划的县与尚未实施该计划的县，比较 1996 年至 2005 年期间浸润性乳腺癌的并发发病率。为了调整乳腺癌发病率时间趋势的变化，还检查了前十年的发病率。通过考虑在 69 岁后停止筛查后发病率的预期下降（方法 1），并通过比较当前筛查组与历史筛查组中 2 岁和 5 岁的女性的发病率，考虑平均领先时间（方法 2），计算过度诊断的百分比。
共纳入 39888 例浸润性乳腺癌患者，其中 7793 例在筛查计划开始后被诊断。对于方法 1，归因于该计划的过度诊断率为 18%至 25%（P<0.001），对于方法 2，过度诊断率为 15%至 20%（P<0.001）。因此，15%至 25%的癌症病例是过度诊断的，这意味着每 2500 名受邀女性中就有 6 至 10 名女性被过度诊断。
该研究是基于登记的。
乳房 X 光筛查会导致大量的过度诊断。
挪威研究理事会和前沿科学。
