Assessment of lifetime gained as a result of mammographic breast cancer screening using a computer model

A computer model for the simulation of breast cancer screening (MBS) is used to calculate the results of screening in terms of lifetime. To optimize breast cancer screening protocols, risk (lifetime lost due to radiation-induced tumours) versus benefit (lifetime gained due to early detection of breast cancer) analyses are performed for a simulated stable Swedish female population. The present study focuses on the results of different screening strategies employing single view mammography, including starting and finishing ages of screening, time interval between successive screening sessions as well as the influence of high detection screening and differences between different populations, based on lifetime lost or gained. To test the stability of the recommendations with respect to possible changes in the variables used in MBS, calculations are also performed for high risk factors for breast tumour induction using both the additive and multiplicative risk models, fast growing breast tumours, late incidence of breast tumours and age dependent survival. The results of the simulations expressed in terms of lifetime gained suggest that a theoretical benefit can be obtained employing starting and finishing ages of 35 and 75 years, respectively. In terms of number of fatal breast tumours, the favourable screening period is 40-80 years. It is concluded that the recommendations are stable for changes in the input variables of MBS. The benefits of higher detection screening are more marked for younger than for older women. A high screening frequency results in more lifetime gained, especially at relatively young ages, whereas for older ages the effect is only marginal.