Additional file 2 Figure S1. Graphical assessment of non-linear relationship of age with contralateral breast cancer risk. Figure S2. Visual assessment of calibration through calibration plots in the internal-external cross-validation at 5 years for the contralateral breast cancer risk model with BRCA mutation information. Figure S3. Visual assessment of calibration through calibration plots in the internal-external cross-validation at 10 years for the contralateral breast cancer risk model with BRCA mutation information. Figure S4. Decision curve analysis at 5 years for the contralateral breast cancer risk model including BRCA1/2 mutation information. Figure S5. Results of the leave-one-study-out cross-validation for the contralateral breast cancer risk model at 5 and 10 years without BRCA mutation information. Figure S6. Visual assessment of calibration through calibration plots in the internal-external cross-validation at 5 years for the contralateral breast cancer risk model without BRCA mutation information. Figure S7. Visual assessment of calibration through calibration plots in the internal-external cross-validation at 10 years for the contralateral breast cancer risk model without BRCA mutation information. Figure S8. Density distribution of 10-year predicted absolute risk in patients with no family history and patients with a family history. Figure S9. Decision curve analysis at 5 years for the contralateral breast cancer risk model without BRCA mutation information. Figure S10. Decision curve analysis at 10 years for the contralateral breast cancer risk model without BRCA mutation information. Figure S11. Assessment of inclusion of information of contralateral preventive mastectomy (CPM).