Cumulative probability of a false-positive screening result in the Finnish breast cancer screening program

The purpose of this thesis is to study the cumulative probability of a false-positive (FP) test result during the Finnish 20-year breast cancer screening program. This study is based on breast cancer screening data provided by the Mass Screening Registry of the Finnish Cancer Registry, which consists of women aged 50–51 years at the time of their first invitation to mammography screening in 1992–1995. Generalized estimating equations (GEE) are used to estimate the cumulative probability of a FP screening result. In the theoretical part we present the corresponding theory together with reviewing the theory of generalized linear models (GLM). The cumulative probabilities are calculated from the modeling of individual examinations by using the theory and formulas of conditional probability. The confidence intervals (Cl) are calculated by using Monte Carlo simulation relying on the asymptotic properties of the GEE estimates. The estimated cumulative risk of at least one FP during the screening program was 15.84% (95% Cl: 15.49–16.18%). Previous FP findings increased the risk of (another) FP results with an odds ratio (OR) of 1.91 (95% Cl: 1.78–2.04), and OR 3.09 (95% Cl: 2.49–3.83) for one or more previous FP results, respectively. Irregular screening attendance increased the risk of FP results with an OR of 1.46 (95% Cl: 1.37–1.56).