Estimating lead time and overdiagnosis in cancer screening programmes : the MOCCI method

Vratanar, Bor (author), Pohar Perme, Maja (author)

Background: Cancer screening enables earlier cancer diagnosis and treatment. The interval between cancer diagnosis by screening and the symptomatic detection in the absence of screening is termed lead time. If a patient's tumour, detected by screening, would never surface clinically, the patient is considered overdiagnosed. Estimating these quantities is crucial for evaluating cancer screening programmes. Development: We developed MOCCI (Minimizing Observed and Counterfactual Cancer Incidence), a novel parametric method for estimating the lead time distribution. MOCCI compares age- and calendar-stratified cancer incidence between individuals invited to screening and those not invited and estimates the lead time distribution that minimizes the incidence difference between the two groups. The probability of overdiagnosis is then estimated by comparing the model-predicted lead time with the time to death from other causes. Application: In an application to the Slovenian breast cancer screening programme, we estimated that 30% (95% confidence interval [CI], 20% to 39%) of screen-detected cases were non-progressive and 33% (95% CI, 25% to 43%) were overdiagnosed; assuming an exponential lead time distribution for progressive cancers, the mean lead time was 1.8 years (95% CI, 1.3 to 2.9). Conclusions: This study proposes a new method for estimating lead time and overdiagnosis. The proposed method (a) can accommodate various lead time distributions, (b) yields a lead time distribution that is aligned with the observed excess incidence arising from screening, and (c) enables the separation of different sources of overdiagnosis. The method provides stable estimates when sample sizes are large and the assumed lead time model is simple.

• Language: English
• Keywords: causal inference, counterfactual, deconvolution, incidence, lead time, overdiagnosis
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine
• Publication version: Version of Record
• Publication date: 01.01.2026
• Year: 2026
• Number of pages: 8 str.
• Numbering: Vol. 55, iss. 5, art. dyag167
• PID: 20.500.12556/RUL-186678
• UDC: 616-006:61:004:519.87
• ISSN on article: 1464-3685
• DOI: 10.1093/ije/dyag167
• COBISS.SI-ID: 288271107
• Publication date in RUL: 04.09.2026

Record is a part of a journal

• Title: International journal of epidemiology
• Shortened title: Int J Epidemiol
• Publisher: Oxford
• ISSN: 1464-3685
• COBISS.SI-ID: 3204116

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: vzročno sklepanje, nasprotno dejstvo, dekonvolucija, incidenca, časovna prednost, prediagnosticiranje

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P3-0429
• Name: Slovenski raziskovalni program za celostno obravnavo raka SLORApro

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P3-0154
• Name: Metodologija za analizo podatkov v medicini