Bulliard Jean-Luc, Sasieni Peter, Klabunde Carrie, De Landtsheer Jean-Pierre, Yankaskas Bonnie C, Fracheboud Jacques
Cancer Epidemiology Unit, University Institute of Social and Preventive Medicine, Lausanne, Switzerland.
Int J Cancer. 2006 Sep 1;119(5):1158-63. doi: 10.1002/ijc.21941.
International comparisons of interval cancers (IC) are important to better understand the relationship between programmes' performance and screening practices. In this respect, differences in (i) definition, (ii) identification and (iii) quantification of IC have received little attention. To examine these 3 comparability issues and activities involving IC, an assessment was conducted among member countries of the International Breast Cancer Screening Network, and the impact of accuracy of identification and quantification practices was estimated using 1996-98 data from the Dutch breast cancer screening programme. Information was obtained from 19 screening programmes in 18 countries, 16 of which acknowledged the coexistence of opportunistic screening. IC data were collected to evaluate performance of the screening programme (100% of programmes) and the radiologists (89%); 53% of programmes had a designated review process for IC. Most programmes (84%) agreed with the European Guidelines definition of IC, but a case situation exercise evidenced substantial discrepancy in classification of cancers that occurred after a positive screen. Completeness of identification of IC appears to contribute most to international variation, and cannot be easily controlled for in methodologically rigorous comparisons. Statistically significant differences of about 4% were measured between quantification methods for IC. An operational definition of IC is proposed to enhance international comparability. Valid comparisons of IC are possible with careful attention to the definition but true differences in IC frequency across screening programmes should exceed 10% to be possibly indicative of real differences between programmes.
对间期癌（IC）进行国际比较，对于更好地理解筛查项目的实施效果与筛查实践之间的关系至关重要。在这方面，间期癌在（i）定义、（ii）识别以及（iii）量化方面的差异很少受到关注。为了研究这三个可比性问题以及与间期癌相关的活动，我们对国际乳腺癌筛查网络的成员国进行了评估，并利用荷兰乳腺癌筛查项目1996 - 1998年的数据估算了识别和量化实践准确性的影响。我们从18个国家的19个筛查项目中获取了信息，其中16个项目承认存在机会性筛查。收集间期癌数据以评估筛查项目（100%的项目）和放射科医生（89%）的表现；53%的项目有针对间期癌的指定复查流程。大多数项目（84%）认同欧洲指南对间期癌的定义，但一项病例情景分析表明，在阳性筛查后发生的癌症分类中存在显著差异。间期癌识别的完整性似乎是造成国际差异的最大因素，在方法严谨的比较中难以轻易控制。间期癌量化方法之间的差异约为4%，具有统计学意义。我们提出了一个间期癌的操作性定义，以提高国际可比性。只要仔细关注定义，就可以对间期癌进行有效的比较，但各筛查项目之间间期癌发生率的真正差异应超过10%，才可能表明项目之间存在实际差异。
