Fig. 1: Geographic variation in genetic risk.

The risk is compared to age-standardised breast cancer incidence. The proportion of women with the breast cancer polygenic risk score (PRS) above the 90th percentile in each region is estimated with respect to the PRS distribution of the whole country. The PALB2 and CHEK2 maps show across different regions the proportion of women carrying at least one risk allele for the variants. The areas represent region of birth obtained from Statistics Finland. The national breast cancer incidence in women was obtained from the Finnish Cancer Registry (publicly available at https://cancerregistry.fi/statistics/) with diagnosis C50 (International Classification of Diseases for Oncology, 3rd edn, ICD-O-3). The incidence represents the mean of 5-year age-standardised incidences (based on the 2014 Finnish population, calculated for each hospital district over 1998–2007). The mean and standard deviation were calculated over the different regions. Variants: rs180177102 (c.1592delT) for PALB2 and rs555607708 (c.1100delC) for CHEK2. CHEK2 and polygenic risk score plots are based on 122,978 women, and PALB2 on 109,371 women. Colour contrasts were chosen approximately based on the standard deviation for each map.