CR-UK Centre for Epidemiology, Mathematics and Statistics, Wolfson Institute for Preventive Medicine, Charterhouse Square, London WC1M 6BQ, UK.
Br J Cancer. 2011 May 24;104(11):1680-5. doi: 10.1038/bjc.2011.144. Epub 2011 May 3.
We analysed 10-year survival data in 19,411 women aged 50-64 years diagnosed with invasive breast cancer in the West Midlands region of the United Kingdom. The aim was to estimate the survival advantage seen in cases that were screen detected compared with those diagnosed symptomatically and attribute this to shifts in prognostic variables or survival differences specific to prognostic categories.
We studied tumour size, histological grade and the Nottingham Prognostic Index in very narrow categories and investigated the distribution of these prognostic factors within screen-detected and symptomatic tumours. We also adjusted for lead time bias.
The unadjusted 10-year breast cancer survival in screen-detected cases was 85.5% and in symptomatic cases 62.8%; after adjustment for lead time bias, survival in the screen-detected cases was 79.3%. Within narrow categories of prognostic variables, survival differences were small, indicating that the majority of the survival advantage of screen detection is due to differences in the distributions of size and node status.
Our results suggested that a combination of lead time with size and node status in 10 categories explained almost all (97%) of the survival advantage. Only a small proportion remained to be explained by biological differences, manifested as length bias or overdiagnosis.
我们分析了英国西米德兰兹地区 19411 名年龄在 50-64 岁之间被诊断患有浸润性乳腺癌的女性的 10 年生存数据。目的是估计筛查发现的病例与症状性诊断的病例之间的生存优势，并将其归因于预后变量的变化或特定于预后类别的生存差异。
我们研究了非常狭窄类别的肿瘤大小、组织学分级和诺丁汉预后指数，并调查了这些预后因素在筛查发现和症状性肿瘤中的分布。我们还调整了领先时间偏倚。
未经调整的筛查发现病例的 10 年乳腺癌生存率为 85.5%，症状性病例为 62.8%；调整领先时间偏倚后，筛查发现病例的生存率为 79.3%。在预后变量的狭窄类别中，生存差异较小，表明筛查发现的生存优势主要归因于大小和淋巴结状态分布的差异。
我们的结果表明，领先时间与 10 个类别的大小和淋巴结状态相结合，几乎可以解释（97%）全部生存优势。只有一小部分可以用生物学差异来解释，表现为长度偏差或过度诊断。
