{"entity":{"id":"lead-time-bias","kind":"term","name":"Lead time, and lead-time bias","aka":["lead time","lead-time","lead time bias","screening lead time","lead time in prostate cancer screening"],"tldr":"Finding a cancer earlier means you know about it for longer, even if nothing you do changes the day you die. That extra stretch of knowing is called the lead time, and lead-time bias is the mistake of counting it as extra life. It is the single biggest reason survival figures make screening look better than it is.","summary":"Lead time is the interval between the moment a screening test finds a cancer and the moment that cancer would have been diagnosed because it caused symptoms. Lead-time bias is what happens when survival is measured from diagnosis: a man whose cancer is found five years earlier appears to survive five years longer even if the date of his death is unchanged. It is why survival from diagnosis is close to useless as a measure of whether a screening programme works, and why randomised screening trials report mortality in the whole invited population instead.\n\nProstate cancer has the longest lead time of any common cancer, and the honest figure is a range rather than a number. Draisma and Etzioni ran three independently built models of prostate cancer progression and detection, all calibrated to Surveillance, Epidemiology, and End Results incidence in United States men aged 54 to 80 between 1985 and 2000. Among screen-detected cancers that would have surfaced in the man's lifetime, mean lead time was 5.4 to 6.9 years across the three models; the original MISCAN model fitted instead to the Rotterdam section of the European screening trial gave 7.9 years. Published estimates before that work spanned 3 to 12 years. The three models agreed closely with each other for any single definition of lead time and disagreed substantially across definitions, which is the paper's real finding: the number is a property of the question, not of the disease.\n\nThe consequence is practical. Lead time is what generates overdiagnosis: if the lead time is longer than the man's remaining life, the cancer would never have troubled him, and the same modelling put overdiagnosis at 23 to 42 percent of screen-detected cancers in the United States calibration and 66 percent in the Rotterdam one. It is also why the 2018 United States task force statement expresses benefit as deaths and metastatic cases prevented per 1,000 men screened over about 13 years rather than as a survival rate, and why the two 2009 randomised trials, ERSPC and PLCO, are the evidence rather than any registry series.","asOf":"2026-09-25","wikipedia":"https://en.wikipedia.org/wiki/Lead_time_bias","links":[{"label":"Draisma et al., Journal of the National Cancer Institute 2009: lead time and overdiagnosis in prostate-specific antigen screening, importance of methods and context","url":"https://doi.org/10.1093/jnci/djp001"},{"label":"Welch and Albertsen, Journal of the National Cancer Institute 2009: prostate cancer diagnosis and treatment after the introduction of prostate-specific antigen screening, 1986 to 2005","url":"https://doi.org/10.1093/jnci/djp278"},{"label":"US Preventive Services Task Force, JAMA 2018: screening for prostate cancer, recommendation statement","url":"https://doi.org/10.1001/jama.2018.3710"},{"label":"Schroder et al., New England Journal of Medicine 2009 (ERSPC): screening and prostate cancer mortality in a randomised European study","url":"https://doi.org/10.1056/nejmoa0810084"}],"tags":["gu","prostate-glossary"],"related":["overdiagnosis","number-needed-to-screen","overtreatment","paper-draisma-lead-time-overdiagnosis-psa-jnci-2009","prostate-screening-psa-mri"],"cancers":["prostate","prostate-low-risk","prostate-intermediate-risk"],"sections":["early-detection","prevention"],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["overdiagnosis","overtreatment","number-needed-to-screen","screening","psa"],"trials":[],"people":[],"bottlenecks":["b-overdiagnosis","b-early-detection","b-trial-design"],"keyPapers":["paper-draisma-lead-time-overdiagnosis-psa-jnci-2009","paper-welch-albertsen-psa-era-diagnosis-treatment-jnci-2009","paper-schroder-erspc-screening-mortality-nejm-2009"],"journals":[],"dependsOn":[],"notes":["Why a five-year survival rate cannot settle a screening argument. Three biases push it up without anyone living longer: lead-time bias, because the clock starts earlier; length bias, because a test that samples the population at intervals preferentially catches slow-growing cancers that sit around waiting to be found; and overdiagnosis, because cancers that would never have surfaced are added to the numerator of survivors. All three run in the same direction. Mortality in a randomised invited population is immune to all three, which is why it is the endpoint the trials used.","Lead time is not the same as overdiagnosis, although the two are produced by the same mechanism. Lead time is how much earlier the diagnosis came. Overdiagnosis is the case where the lead time exceeded the rest of the man's life, so the diagnosis never needed to come at all. A long lead time with a long life left is exactly what screening is for."],"category":"Epidemiology & prevention"},"route":"/terms/lead-time-bias/","neighbours":{"term":[{"id":"number-needed-to-screen","kind":"term","name":"Number needed to screen (and number needed to diagnose)","route":"/terms/number-needed-to-screen/"},{"id":"overdiagnosis","kind":"term","name":"Overdiagnosis","route":"/terms/overdiagnosis/"},{"id":"overtreatment","kind":"term","name":"Overtreatment","route":"/terms/overtreatment/"},{"id":"polygenic-risk-score","kind":"term","name":"Polygenic risk score (PRS)","route":"/terms/polygenic-risk-score/"},{"id":"psa","kind":"term","name":"PSA (prostate-specific antigen)","route":"/terms/psa/"},{"id":"screening","kind":"term","name":"Screening","route":"/terms/screening/"}],"paper":[{"id":"paper-schroder-erspc-screening-mortality-nejm-2009","kind":"paper","name":"ERSPC: screening and prostate cancer mortality in a randomised European study","route":"/key-papers/paper-schroder-erspc-screening-mortality-nejm-2009/"},{"id":"paper-draisma-lead-time-overdiagnosis-psa-jnci-2009","kind":"paper","name":"Lead time and overdiagnosis in prostate-specific antigen screening: importance of methods and context","route":"/key-papers/paper-draisma-lead-time-overdiagnosis-psa-jnci-2009/"},{"id":"paper-catalona-psa-screening-test-nejm-1991","kind":"paper","name":"Measurement of prostate-specific antigen in serum as a screening test for prostate cancer","route":"/key-papers/paper-catalona-psa-screening-test-nejm-1991/"},{"id":"paper-loeb-overdiagnosis-overtreatment-prostate-eur-urol-2014","kind":"paper","name":"Overdiagnosis and overtreatment of prostate cancer","route":"/key-papers/paper-loeb-overdiagnosis-overtreatment-prostate-eur-urol-2014/"},{"id":"paper-andriole-plco-prostate-screening-nejm-2009","kind":"paper","name":"PLCO: mortality results from a randomised prostate cancer screening trial","route":"/key-papers/paper-andriole-plco-prostate-screening-nejm-2009/"},{"id":"paper-welch-albertsen-psa-era-diagnosis-treatment-jnci-2009","kind":"paper","name":"Prostate cancer diagnosis and treatment after the introduction of prostate-specific antigen screening, 1986 to 2005","route":"/key-papers/paper-welch-albertsen-psa-era-diagnosis-treatment-jnci-2009/"},{"id":"paper-moyer-uspstf-prostate-screening-ann-intern-med-2012","kind":"paper","name":"USPSTF 2012: screening for prostate cancer, recommendation statement (grade D)","route":"/key-papers/paper-moyer-uspstf-prostate-screening-ann-intern-med-2012/"}],"technology":[{"id":"prostate-screening-psa-mri","kind":"technology","name":"PSA and MRI-first prostate cancer screening","route":"/technologies/prostate-screening-psa-mri/"}],"cancer":[{"id":"prostate-intermediate-risk","kind":"cancer","name":"Localised prostate cancer, intermediate risk","route":"/cancers/prostate-intermediate-risk/"},{"id":"prostate-low-risk","kind":"cancer","name":"Localised prostate cancer, very low and low risk","route":"/cancers/prostate-low-risk/"},{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"section":[{"id":"early-detection","kind":"section","name":"Early Detection & Screening","route":"/fronts/early-detection/"},{"id":"prevention","kind":"section","name":"Prevention & Risk","route":"/fronts/prevention/"}],"bottleneck":[{"id":"b-overdiagnosis","kind":"bottleneck","name":"Overdiagnosis and false alarms","route":"/bottlenecks/b-overdiagnosis/"},{"id":"b-early-detection","kind":"bottleneck","name":"The hardest cancers are found late","route":"/bottlenecks/b-early-detection/"},{"id":"b-trial-design","kind":"bottleneck","name":"Trial design, endpoints and cost","route":"/bottlenecks/b-trial-design/"}],"idea":[{"id":"idea-prostate-metastatic-presentation-as-the-screening-endpoint","kind":"idea","name":"Judge a prostate screening programme on metastatic presentation, not on incidence or mortality","route":"/ideas/idea-prostate-metastatic-presentation-as-the-screening-endpoint/"}]}}