University of Tampere, School of Public Health, Tampere, Finland.
Eur J Cancer. 2010 Nov;46(17):3102-8. doi: 10.1016/j.ejca.2010.09.034.
Lead-time is defined as the time by which screening advances the diagnosis compared with absence of screening. A sufficiently long lead-time needs to be achieved so that cancer can be detected while still curable. A very short lead-time may indicate poor sensitivity of the screening test, while a very long lead-time suggests overdiagnosis.
In the first screening round, a total of 56,294 men aged 55-74 years were screened with serum prostate specific antigen (PSA) in five countries of the European Randomised Study of Screening for Prostate Cancer (ERSPC) with an overall detection rate (prevalence) of 2.8% (1972 prostate cancers). Prostate cancer incidence among 92,142 men randomly allocated to the control arm of the trial was also assessed. Lead-time was estimated as the time required to accumulate a similar cumulative risk of prostate cancer in the control arm to the detection rate in the intervention arm, i.e. from the ratio of detection rate (prevalence of screen-detected cases) and expected incidence (cumulative risk).
Using a serum PSA cut-off of 4 ng/ml, the mean lead-time in the whole study population was estimated as 6.8 years (95% confidence interval (95% CI) 7.9-8.4). It was 8 years in The Netherlands, 6 in Sweden and Finland, 5 in Italy and 4 in Belgium. The mean lead-time was similar, 6-7 years, at ages 50-64 years, but close to 8 years among men aged 65-74 years. A lower PSA cut-off level of 3 ng/ml used in Sweden and The Netherlands prolonged the mean lead-time by approximately 1 year. Lead-time based on advanced prostate cancer only was slightly shorter, mean 5.3 years (95% CI 4.6-6.0). The lead-time for the second screening round was slightly shorter than that for the first (5.9, 95% CI 5.4-6.4), reflecting a similar relation between detection rate and control group incidence.
The lead-time for prostate cancer found in ERSPC substantially exceeded that found for breast, cervical and colorectal cancer screening. One round of prostate cancer screening can advance clinical diagnosis by 4-8 years. Overdiagnosis or detection of non-progressive tumours may contribute substantially to the lead-time.
领先时间定义为筛查相对于无筛查而言提前诊断的时间。需要达到足够长的领先时间，以便在癌症仍可治愈时发现癌症。非常短的领先时间可能表明筛查试验的灵敏度差，而非常长的领先时间则表明过度诊断。
在第一轮筛查中，共有 56294 名 55-74 岁的男性在欧洲前列腺癌筛查随机研究（ERSPC）的五个国家接受了血清前列腺特异性抗原（PSA）筛查，总检出率（患病率）为 2.8%（1972 例前列腺癌）。还评估了随机分配到试验对照组的 92142 名男性的前列腺癌发病率。领先时间估计为在对照组中积累与干预组检测率相似的累积前列腺癌风险所需的时间，即从检测率（筛查发现病例的患病率）与预期发病率（累积风险）的比值计算得出。
使用 PSA 截断值为 4ng/ml，整个研究人群的平均领先时间估计为 6.8 年（95%置信区间（95%CI）7.9-8.4）。荷兰为 8 年，瑞典和芬兰为 6 年，意大利为 5 年，比利时为 4 年。50-64 岁年龄组的平均领先时间相似，为 6-7 年，但 65-74 岁年龄组的平均领先时间接近 8 年。在瑞典和荷兰使用的 PSA 截断值较低（3ng/ml），使平均领先时间延长了约 1 年。仅基于晚期前列腺癌的领先时间略短，平均为 5.3 年（95%CI 4.6-6.0）。第二轮筛查的领先时间略短于第一轮（5.9，95%CI 5.4-6.4），反映了检测率与对照组发病率之间的相似关系。
ERSPC 发现的前列腺癌的领先时间大大超过了乳腺癌、宫颈癌和结直肠癌筛查的领先时间。一轮前列腺癌筛查可以使临床诊断提前 4-8 年。过度诊断或检测非进展性肿瘤可能会大大增加领先时间。
