Use of microsimulation modeling for research in breast cancer screening

Prospective clinical trials on breast cancer screening take many years to provide results and are very costly. It is simply not feasible to answer all important questions by conducting a study. In addition, there are many inter-related variables that can affect screening outcomes and it is often not possible to study these individually through trials. Microsimulation modeling provides a practical alternative which allows the estimates of different key outcomes of screening in response to changes in the underlying human and technical variables. OncoSim Breast is part of a suite of specialized cancer microsimulation models developed by Statistics Canada in collaboration with The Canadian Partnership Against Cancer. The model simulates a cohort of women from birth to death through individual histories. At its heart is a mathematical function describing tumor growth. As women progress through life, at each time point, calculations are performed through random number selection, weighted by empirical probability data for each phenomenon in the simulation. The model is adapted to a particular problem by creating "scenarios" specifying the assumptions regarding the members of the cohort and any screening intervention(s) and treatment. We demonstrate how it can be helpful in optimizing screening regimens, predicting the impact of technical innovations and improvements and studying other problems where trials would be difficult or impossible to perform.