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UBC Theses and Dissertations

Statistical modelling of breast cancer risk for British Columbian women Hoegg, Tanja


Although there are many known factors associated with an increased risk of breast cancer, age remains the main eligibility criterion for the current Screening Mammography Program of British Columbia (SMP BC). In the light of recent controversy surrounding regular breast screening, the ability of targeted screening for high-risk women is of current interest as it has the potential to sustain high cancer detection rates, reduce the number of false positive results while controlling the overall costs. Multiple models have been proposed to estimate a woman’s risk of breast cancer given her current risk factor profile, the model introduced by Gail et al. in 1989 being particularly popular. Using five-year follow-up data of 223,399 SMP BC participants, we investigate whether the probability estimates of the Gail model adequately stratify the British Columbian population into groups of high and low-risk women and, hence, provide a basis for a personalized access criterion into the Screening Mammography Program. Further, we built a breast cancer risk model for British Columbia with the goal to include a stronger set of predictor variables and improve the outcome stratification of the Gail model. Neither the Gail model nor the new risk prediction model based on SMP BC participants showed adequate stratification properties. Overall, effect sizes of all covariates were too small to clearly separate risk estimates of future breast cancer cases and non-cases. It is questionable whether changes in screening policies should be based on breast cancer risk prediction models.

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