Lund Eiliv, Mode Nicolle, Waaseth Marit, Thalabard Jean-Christophe
Department of Community Medicine, Faculty of Health Sciences, University of Tromsø - The Arctic University of Norway, Tromsø, Norway.
BMC Cancer. 2013 Dec 30;13:614. doi: 10.1186/1471-2407-13-614.
There is increasing ambiguity towards national mammographic screening programs due to varying publicized estimates of overdiagnosis, i.e., breast cancer that would not have been diagnosed in the women's lifetime outside screening. This analysis compares the cumulative incidence of breast cancer in screened and unscreened women in Norway from the start of the fully implemented Norwegian Breast Cancer Screening Program (NBCSP) in 2005.
Subjects were 53 363 women in the Norwegian Women and Cancer (NOWAC) study, aged 52-79 years, with follow-up through 2010. Mammogram and breast cancer risk factor information were taken from the most recent questionnaire (2002-07) before the start of individual follow-up. The analysis differentiated screening into incidence (52-69 years) and post screening (70-79 years). Relative risks (RR) were estimated by Poisson regression.
The analysis failed to detect a significantly increased cumulative incidence rate in screened versus other women 52-79 years. RR of breast cancer among women outside the NBCSP, the "control group", was non-significantly reduced by 7% (RR=0∙93; 95% confidence interval 0∙79 to 1∙10) compared to those in the program. The RR was attenuated when adjusted for risk factors; RRadj=0∙97 (0∙82 to 1∙15). The control group consisted of two subpopulations, those who only had a mammogram outside the program (RRadj =1∙04; 0∙86 to 1∙26) and those who never had a mammogram (RRadj=0∙77; 0∙59 to 1∙01). These groups differed significantly with respect to risk factors for breast cancer, partly as a consequence of the prescription rules for hormone therapy which indicate a mammogram.
In the fully implemented NBCSP, no significant difference was found in cumulative incidence rates of breast cancer between NOWAC women screened and not screened. Naïve comparisons of screened and unscreened women may be affected by important differences in risk factors. The current challenge for the screening program is to improve the diagnostics used at prevalence screenings (ages 50-51).
由于公开的过度诊断估计值各不相同，即那些在没有筛查的情况下女性一生中不会被诊断出的乳腺癌，人们对国家乳腺钼靶筛查计划的模糊认识日益增加。本分析比较了自2005年挪威全面实施乳腺癌筛查计划（NBCSP）开始以来，挪威接受筛查和未接受筛查女性的乳腺癌累积发病率。
研究对象为挪威女性与癌症（NOWAC）研究中的53363名女性，年龄在52 - 79岁之间，随访至2010年。乳腺钼靶检查和乳腺癌风险因素信息取自个体随访开始前的最新调查问卷（2002 - 2007年）。分析将筛查分为发病期（52 - 69岁）和筛查后期（70 - 79岁）。相对风险（RR）通过泊松回归进行估计。
该分析未能检测出52 - 79岁接受筛查女性与其他女性相比，累积发病率有显著增加。与参与该计划的女性相比，NBCSP之外的女性，即“对照组”，患乳腺癌的RR无显著降低，降低了7%（RR = 0.93；95%置信区间0.79至1.10）。在对风险因素进行调整后，RR减弱；RRadj = 0.97（0.82至1.15）。对照组由两个亚组组成，即那些仅在计划外进行过一次乳腺钼靶检查的女性（RRadj = 1.04；0.86至1.26）和那些从未进行过乳腺钼靶检查的女性（RRadj = 0.77；0.59至1.01）。这些组在乳腺癌风险因素方面存在显著差异，部分原因是激素治疗的处方规定会建议进行乳腺钼靶检查。
在全面实施的NBCSP中，NOWAC研究中接受筛查和未接受筛查的女性之间，乳腺癌累积发病率未发现显著差异。对接受筛查和未接受筛查女性的简单比较可能会受到风险因素重要差异的影响。筛查计划当前面临的挑战是改进在普查（50 - 51岁）时所使用的诊断方法。
