additional discussion of chapter 3
An investigation of design and bias issues in case-control studies of cancer screening using microsimulation

While the article of this chapter shows that there is an innate source of bias in the method of case-control studies on mortality effects of cancer screening, the question arises: can this bias be removed?
The problem would be solved if for screendetected cases the window in which exposure of the matched controls is measured would be extended with the lead-time of the case. This lead-time cannot be known for individual cases, but it can be estimated. A similar investigation as described in this chapter can be applied to an exposure measure that would extend exposure measure B with an estimate of the lead-time. This research is currently being carried out.
Another problem that remains is the bias caused by an association between attendance to screening and the risk of acquiring breast cancer and/or survival from breast cancer. It has been shown that this source of bias can be considerably larger than that described in the article of this chapter.(Gullberg et al. 1991) The approach of that article can also be applied to research bias in case control studies that arises from an assumed association between attendance to screening and the risk of acquiring breast cancer or survival from breast cancer. Also this research is currently being carried out.