Fig. 3. Absolute contralateral breast cancer risk by PRS percentiles per age category of the first breast cancer diagnosis for BRCA1 and BRCA2 heterozygotes.

Predicted absolute contralateral breast cancer risks by percentile of the continuous ER-negative PRS₃₁₃ for BRCA1 heterozygotes and ER-positive PRS₃₁₃ for BRCA2 heterozygotes. The assumed contralateral breast cancer incidences were from a study that estimated breast cancer incidence in a large prospective cohort of BRCA1 and BRCA2 heterozygotes.²⁰ The age categories were based on the age at diagnosis of the first primary breast tumor. Risks were calculated including the interaction between the PRS and the continuous age of first breast cancer diagnosis. The lines for different percentiles of the PRS are overlapping for the age category ≥50 year for BRCA1 heterozygotes. BC breast cancer, CBC contralateral breast cancer, PRS polygenic risk score.