Michalopoulos Dimitrios, Duffy Stephen W
Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary, University of London, London, UK.
Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary, University of London, London, UK
J Med Screen. 2016 Dec;23(4):192-202. doi: 10.1177/0969141315623980. Epub 2016 Mar 2.
Estimating overdiagnosis in cancer screening is complicated. Using observational data, estimation of the expected incidence in the screening period and taking account of lead time are two major problems.
Using data from the Cancer Registry of Norway and the Norwegian Breast Cancer Screening Programme, we estimated incidence trends, using age-specific trends by year in the pre-screening period (1985-95). We also estimated sojourn time and sensitivity using interval cancers only. Thus, lead time estimates were uncontaminated by overdiagnosed cases. Finally, we derived estimates of overdiagnosis separately for all cancers, and for invasive cancers only, correcting for lead time, using two different methods.
Our results indicate that overdiagnosis of all cancers, invasive and in situ, constituted 15-17% of all screen-detected cancers in 1996-2009. For invasive cancers only, the corresponding figures were -2 to 7% in the same period, suggesting that a substantial proportion of the overdiagnosis in the Norwegian Programme was due to ductal carcinoma in situ.
Using short-term trends, instead of long, prior to screening was more effective in predicting incidence in the screening epoch. In addition, sojourn time estimation using symptomatic cancers only avoids over-correction for lead time and consequently underestimation of overdiagnosis. Longer follow-up will provide more precise estimates of overdiagnosis.
估计癌症筛查中的过度诊断情况很复杂。利用观察性数据，估计筛查期间的预期发病率以及考虑领先时间是两个主要问题。
我们利用挪威癌症登记处和挪威乳腺癌筛查计划的数据，通过筛查前时期（1985 - 1995年）各年龄段逐年的趋势来估计发病率趋势。我们还仅使用间期癌来估计停留时间和敏感度。因此，领先时间估计未受过度诊断病例的影响。最后，我们使用两种不同方法，分别针对所有癌症以及仅针对浸润性癌症，在校正领先时间后得出过度诊断的估计值。
我们的结果表明，在1996 - 2009年期间，所有癌症（包括浸润性和原位癌）的过度诊断占所有筛查发现癌症的15% - 17%。仅对于浸润性癌症，同期相应数字为 - 2%至7%，这表明挪威筛查计划中相当一部分过度诊断是由导管原位癌导致的。
在筛查前使用短期趋势而非长期趋势能更有效地预测筛查时期的发病率。此外，仅使用有症状癌症来估计停留时间可避免对领先时间的过度校正，从而避免对过度诊断的低估。更长时间的随访将提供更精确的过度诊断估计值。
