A note on the sensitivities of self-reporting and screen detection of primary breast tumours

Screening programs for breast cancer are widely used to reduce the impact of breast cancer in populations. For example, the South Australian Breast X-ray Service, BreastScreen SA, established in 1989, is a participant in the National Program of Early Detection of Breast Cancer. BreastScreen SA has collected information on both screening-detected and interval or self-reported cases, which enables the estimation of various important attributes of the screening mechanism. In this paper, a tailored model is fitted to the BreastScreen SA data. The probabilities that the screening detects a tumour of a given size and that an individual reports a tumour by a specified size in the absence of screening are estimated. Estimates of the distribution of sizes detected in the absence of screening, and at the first two screenings, are also given.