Background: Breast cancer screening traditionally uses only age as an inclusion criterium and screening protocol is unique for all participants. Not all women are at the same breast cancer risk and many breast cancer risk factors are well known. The evidence shows that risk-based strategy could be implemented to avoid unnecessary harm in mammography screening for breast cancer using age-only criterium. A personalised approach can tailor screening strategies according to women's risk and thus avoid unnecessary harms of screening for women at low risk and offer intensified screening for those at higher risk.
In Slovenia, women with population breast cancer risk are invited to organized national screening programme. Besides, legal and professional backgrounds for personalised screening are in place, but are not organized on a population level, only in opportunistic setting. The proportion of women with much lower or much higher breast cancer risk, that requires tailored screening, is not known for Slovenian women population.
Our study aimed at identifying the breast cancer risk prevalence of Slovenian women, invited to organised screening programme for the first time, and assessing the number of screening mammographies together with different screening protocols in case of risk-based screening.
Methods: A cross-sectional population-based study enrolled 11,898 women without breast cancer diagnosis at the age of 50, invited to breast cancer screening. For study analysis, women who signed informed consent and fullfilled the study questionnaires were included. The data on breast cancer risk factors, including mammographic breast density was collected and breast cancer risk was assessed for each individual using the S-IBIS programme. The S-IBIS is in fact the IBIS programme, adopted to Slovenian breast cancer burden circumstances. It includes Tyrer-Cuzick algorithm (version 8) with Slovenian generation-specific population breast cancer risk. According to S-IBIS risk calculation, women were classified into 10-year and lifetime risk groups (low, population, moderately increased, and high risk group). The same calculation was performed for the same group of women at the age of 40, adjusting the risk factors. The number of screening mammographies according to the risk stratification was simulated.
Results: Out of 11,898 invited, 57.0% (6,785) of women returned breast cancer risk questionnaires. After calculating risk and stratifying women into risk groups, 32.9% were assessed with low, 62.8% with population, 3.7% with moderately increased, and 0.6% with high 10-year breast cancer risk; 97.5% were assessed with population, 2.5% with moderately increased, and 0.04% with high lifetime breast cancer risk. At the age of 40, potentially 9.9% women with moderately increased, and 0.3% with high 10-year breast cancer risk would be recognised. In the case of potential personalised screening in the same group of women from the age 40 till 74, the number of screening mammographies would drop by 33.1% compared to the current screening policy.
Conclusions: The study uptake showed the feasibility of risk assessment when inviting women to regular BC screening. 4.3% of Slovenian women at 50 years of age were recognised with higher than population 10-year breast cancer risk. According to Slovenian BC guidelines they may be screened more often. Overall, personalised screening would decrease the number of screening mammographies in Slovenia. This information is to be considered when planning the pilot and assessing the feasibility of implementing population risk-based screening, if personalised screening would be scientifically proven and recommended at the European level.
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