Table 2.

Adjusted hazard ratios and 95% confidence intervals from Cox proportional hazards modeling of smoking status

		Overall BC			ER-positive BC			ER-negative BC
Continuous FRP	Person years	BC	Model 1a	Model 2b	BC	Model 1a	Model 2b	BC	Model 1a	Model 2b
			HR (95% CI)	HR (95% CI)		HR (95% CI)	HR (95% CI)		HR (95% CI)	HR (95% CI)
Never smoker c	102,781.5	559	Reference	Reference	235	Reference	Reference	85	Reference	Reference
Former smoker	47,088.8	302	1.06 (0.92, 1.22)	1.14 (0.96, 1.34)	118	0.97 (0.77, 1.21)	1.09 (0.84, 1.43)	39	0.95 (0.63, 1.41)	0.92 (0.59, 1.45)
Current smoker	26,466.7	137	1.02 (0.85, 1.23)	0.92 (0.73, 1.15)	54	1.04 (0.77, 1.40)	1.05 (0.73, 1.51)	27	1.22 (0.78, 1.91)	0.81 (0.46, 1.43)
Former smoker*FRP				0.91 (0.81, 1.02)			0.84 (0.68, 1.05)			1.02 (0.85, 1.22)
Current smoker*FRP				1.16 (0.99, 1.35)			0.99 (0.74, 1.32)			1.36 (1.08, 1.71)
Categorical FRP			1-year FRP < 0.34%	1-year FRP ≥ 0.34%		1-year FRP < 0.34%	1-year FRP ≥ 0.34%		1-year FRP < 0.34%	1-year FRP ≥ 0.34%
			HR (95% CI)	HR (95% CI)		HR (95% CI)	HR (95% CI)		HR (95% CI)	HR (95% CI)
Never smoker			Reference	Reference		Reference	Reference		Reference	Reference
Former smoker			1.11 (0.87, 1.43)	1.03 (0.87, 1.23)		0.97 (0.65, 1.45)	0.98 (0.74, 1.28)		0.80 (0.31, 2.04)	0.94 (0.61, 1.44)
Current smoker			0.91 (0.64, 1.28)	1.09 (0.87, 1.37)		0.90 (0.52, 1.57)	1.13 (0.79, 1.61)		0.87 (0.29, 2.67)	1.18 (0.72, 1.93)

BC breast cancer, HR hazard ratio, CI confidence interval, ER estrogen receptor expression, FRP familial risk profile

^aModel 1 = Adjusted Cox models which are stratified by birth cohort (< 1950, 1950–1959, 1960–1969, ≥ 1970) and adjusted for study site, race/ethnicity, body mass index, education, and hormonal birth control use

^bModel 2 = Interaction models that include an interaction term with FRP as estimated by 1-year BOADICEA risk score

^cSmokers are defined as having smoked at least one cigarette per day for 3 months or longer