Evolution of the Excess Absolut Risk (ear) in the Valencian Breast Cancer Screening Programme

Breast cancer is one of the most frequent diseases in women, with a high incidence rate. The best fight against the breast cancer is the early detection by means of mammograms in a screening programme. The Valencian Breast Cancer Screening Programme (VBCSP) started at 1992, and it is composed of twenty-two mammography units. The programme is targeted towards asymptomatic women from 45 to 69 years old, but this screening has a negative influence in the studied woman, whatever the diagnosis was. By means of MCNP-4c2 Monte Carlo code, some conversion factors from air kerma to glandular dose have been developed. Different breast woman models, according to the Valencian breast anathomy (taking into account the relation breast radius / breast compression thickness obtained from real samples), have been simulated in order to obtain the glandular breast dose values. Quality control parameters as ESAK values were also employed for developing the methods. The conversion factors give a simple and fast way to obtain the mean glandular dose from mammography exposition parameters. The glandular dose has been also calculated following the European Protocol on Dosimetry in order to compare the results of the new methodology. Four sample populations of 100 women from each unit of the VBCSP have been taken in order to estimate the mean glandular dose and the associated excess absolute risk (EAR). Once the doses for each woman from the samples are obtained and according to the age of them, the EAR value for each sample has been determined following the UNSCEAR 2000 projection risk model, which takes into account the characteristics of the Valencian population and gives the EAR for radio-induced breast cancer. The results have been calculated and compared by means of the ASQRAD software, but with an older risk projection model, the UNSCEAR 1994. Once the four sample average EAR have been calculated, the evolution of the induced risk in the Valencian Breast Cancer Programme has been determined.