Duffy Stephen W, Agbaje Olorunsola, Tabar Laszlo, Vitak Bedrich, Bjurstam Nils, Björneld Lena, Myles Jonathan P, Warwick Jane
Cancer Research UK Department of Epidemiology, Mathematics and Statistics, Wolfson Institute of Preventive Medicine, Queen Mary College, University of London, London, UK.
Breast Cancer Res. 2005;7(6):258-65. doi: 10.1186/bcr1354. Epub 2005 Nov 10.
Randomised controlled trials have shown that the policy of mammographic screening confers a substantial and significant reduction in breast cancer mortality. This has often been accompanied, however, by an increase in breast cancer incidence, particularly during the early years of a screening programme, which has led to concerns about overdiagnosis, that is to say, the diagnosis of disease that, if left undetected and therefore untreated, would not become symptomatic. We used incidence data from two randomised controlled trials of mammographic screening, the Swedish Two-county Trial and the Gothenburg Trial, to establish the timing and magnitude of any excess incidence of invasive disease and ductal carcinoma in situ (DCIS) in the study groups, to ascertain whether the excess incidence of DCIS reported early in a screening trial is balanced by a later deficit in invasive disease and provide explicit estimates of the rate of 'real' and non-progressive 'overdiagnosed' tumours from the study groups of the trials. We used a multistate model for overdiagnosis and used Markov Chain Monte Carlo methods to estimate the parameters. After taking into account the effect of lead time, we estimated that less than 5% of cases diagnosed at prevalence screen and less than 1% of cases diagnosed at incidence screens are being overdiagnosed. Overall, we estimate overdiagnosis to be around 1% of all cases diagnosed in screened populations. These estimates are, however, subject to considerable uncertainty. Our results suggest that overdiagnosis in mammography screening is a minor phenomenon, but further studies with very large numbers are required for more precise estimation.
随机对照试验表明，乳腺钼靶筛查政策可显著降低乳腺癌死亡率。然而，这一政策往往伴随着乳腺癌发病率的上升，特别是在筛查项目开展的早期阶段，这引发了对过度诊断的担忧，也就是说，诊断出的疾病如果未被发现因而未得到治疗，就不会出现症状。我们利用乳腺钼靶筛查的两项随机对照试验（瑞典双县试验和哥德堡试验）的发病率数据，来确定研究组中浸润性疾病和导管原位癌（DCIS）任何额外发病率的时间和幅度，以确定筛查试验早期报告的DCIS额外发病率是否会被后期浸润性疾病的减少所平衡，并明确估计试验研究组中“真正的”和非进展性“过度诊断”肿瘤的发生率。我们使用了一个多状态过度诊断模型，并采用马尔可夫链蒙特卡罗方法来估计参数。在考虑了提前期的影响后，我们估计，在患病率筛查中诊断出的病例中，不到5%被过度诊断，在发病率筛查中诊断出的病例中，不到1%被过度诊断。总体而言，我们估计过度诊断约占筛查人群中所有诊断病例的1%。然而，这些估计存在相当大的不确定性。我们的结果表明，乳腺钼靶筛查中的过度诊断是一个小现象，但需要进行更多非常大规模的研究才能进行更精确的估计。
