Table 1.

Association between PRSs and Contralateral Breast Cancer Risk in the European Cohort (N = 56,068)

Polygenic Risk Score (PRS)	No. of CBC	HR per Unit SDa	95%CI	p Value
PRS77b
All CBC	1,027	1.21	1.14–1.29	<.001
Invasive CBC	923	1.21	1.13–1.29	<.001
PRS313b
All CBC	1,027	1.25	1.18–1.33	<.001
Invasive CBC	923	1.24	1.16–1.32	<.001
ER-positive invasive CBCd	275	1.38	1.23–1.55	<.001
ER-negative invasive CBCd	97	0.92	0.75–1.12	.39
ER-Positive PRS313b,c
All CBC	1,027	1.23	1.16–1.31	<.001
Invasive CBC	923	1.22	1.15–1.30	<.001
ER-positive invasive CBCd	275	1.37	1.22–1.54	<.001
ER-Negative PRS313b,c
All CBC	1,027	1.25	1.17–1.33	<.001
Invasive CBC	923	1.24	1.16–1.33	<.001
ER-negative invasive CBCd	97	1.06	0.86–1.30	.58

Abbreviations: PRS, polygenic risk score; No., number; CBC, contralateral breast cancer; HR, hazard ratio; CI, confidence interval; ER, estrogen receptor; SD, standard deviation.

^aAll analyses were performed with attained age as timescale.

^bCoefficients to construct the PRSs are shown in Table S3. All PRSs were standardized by the same SD as was used by Mavaddat et al.⁷ The SD was 0.45 for overall breast cancer PRS₇₇, 0.61 for overall breast cancer PRS₃₁₃, 0.65 for ER-positive PRS₃₁₃, and 0.59 for ER-negative PRS₃₁₃.

^cER-specific PRSs were constructed using a hybrid method, as described by Mavaddat et al.⁷

^dWomen with ER-unknown CBC (N = 551) were censored in these analyses.