Table 3.

Comparison of expected and observed cases of invasive breast cancer, and hazard ratios for observed cases, according to Gail model predicted 5-year risk for all women by age group, and for group level risk quintiles (Q1 to Q5) and, within Q5, the upper two deciles of risk (D9 and D10)

Age (years)	Quantile group	Predicted 5-year risk (range)	No. of women	Observed (O) breast cancers	Expected (E) breast cancers	Person-years (PY)	O per 10,000 PY	E/0 (95% CI)a	HR (95% CI), p value (Q3 referent)	HR (95% CI), p value (Q1 referent)b
50–69	Q1	0.6–1.1%	8041	72	65	34,078	21	0.90 (0.71–1.15)	0.59 (0.44–0.79), p < 0.0001	Referent
	Q2	1.1–1.4%	8096	77	86	34,160	23	1.12 (0.89–1.42)	0.63 (0.47–0.84), p = 0.001	1.07 (0.78–1.48), p = 0.679
	Q3	1.4–1.7%	8124	122	105	34,264	36	0.86 (0.72–1.04)	Referent	1.70 (1.27–2.27), p < 0.0001
	Q4	1.7–2.3%	7902	132	131	33,254	40	0.99 (0.84–1.19)	1.11 (0.87–1.43), p = 0.388	1.89 (1.42–2.52), p < 0.0001
	Q5	2.3–22.0%	7995	161	225	33,690	48	1.40 (1.20–1.64)	1.34 (1.06–1.70), p = 0.014	2.28 (1.73–3.02), p < 0.0001
	D9	2.3–3.0%	3980	78	88	16,790	46	1.13 (0.91–1.43)	1.30 (0.98–1.73), p = 0.068	2.21 (1.61–3.05), p < 0.0001
	D10	3.0–22.0%	4015	83	137	16,900	49	1.65 (1.33–2.07)	1.39 (1.05–1.83), p = 0.022	2.35 (1.72–3.23), p < 0.0001
	Total	0.2–21.7%	40,158	564	612	169,445	33	1.09 (1.00–1.18)
50–59	Q1	0.6–1.1%	4046	35	29	17,131	20	0.83 (0.60–1.19)	0.83 (0.53–1.30), p = 0.413	Referent
	Q2	1.1–1.4%	4054	33	38	17,167	19	1.14 (0.81–1.66)	0.78 (0.49–1.23), p = 0.283	0.94 (0.58–1.51), p = 0.797
	Q3	1.4–1.7%	4062	42	46	17,117	25	1.10 (0.81–1.52)	Referent	1.21 (0.77–1.89), p = 0.413
	Q4	1.7–2.3%	4013	67	58	16,917	40	0.87 (0.68–1.12)	1.61 (1.10–2.37), p = 0.015	1.95 (1.29–2.93), p = 0.001
	Q5	2.3–13.9%	4041	67	94	17,057	39	1.40 (1.10–1.80)	1.60 (1.09–2.35), p = 0.017	1.93 (1.28–2.90), p = 0.002
	D9	2.1–2.5%	2028	30	38	8567	35	1.28 (0.89–1.89)	1.43 (0.89–2.28), p = 0.138	1.72 (1.06–2.80), p = 0.029
	D10	2.5–13.9%	2013	37	55	8490	44	1.49 (1.08–2.12)	1.77 (1.14–2.76), p = 0.011	2.14 (1.35–3.40), p = 0.001
	Total	0.2–21.7%	20,216	244	264	85,388	29	1.08 (0.96–1.23)
60–69	Q1	0.9–1.1%	4026	41	39	17,022	24	0.96 (0.71–1.34)	0.64 (0.43–0.95), p = 0.026	Referent
	Q2	1.1–1.4%	3992	55	48	16,833	33	0.88 (0.68–1.17)	0.87 (0.61–1.25), p = 0.458	1.36 (0.91–2.04), p = 0.134
	Q3	1.4–1.7%	4041	64	59	17,069	37	0.92 (0.72–1.19)	Referent	1.56 (1.06–2.31), p = 0.026
	Q4	1.7–2.3%	3946	74	75	16,573	45	1.02 (0.81–1.30)	1.19 (0.85–1.67), p = 0.302	1.86 (1.27–2.73), p = 0.0001
	Q5	2.3–22.0%	3937	86	126	16,560	52	1.47 (1.19–1.84)	1.40 (1.01–1.93), p = 0.044	2.18 (1.50–3.16), p < 0.0001
	D9	2.8–3.3%	1953	40	50	8192	49	1.24 (0.91–1.74)	1.31 (0.88–1.94), p = 0.182	2.04 (1.32–3.16), p = 0.001
	D10	3.3–22.0%	1984	46	77	8368	55	1.66 (1.25–2.27)	1.48 (1.01–2.16), p = 0.042	2.31 (1.52–3.53), p < 0.0001
	Total	0.2–21.7%	19,942	320	348	84,057	38	1.09 (0.97–1.22)

CI confidence interval, D, decile, HR hazard ratio, Q quintile

^a Chi-squared test across Q1–Q5 (O vs E) were: χ²= 23.0, p = 0.0001 for women 50–69 years old; χ² = 11.0, p = 0.0262 for women 50–59 years old; and χ² = 14.4, p = 0.0063 for women 60–69 years old

^b Log rank tests for trend across hazard functions Q1–Q5 were χ² = 52, p < 0.0001 for women 50–69 years old; χ² = 20, p < 0.0001 for women 50–59 years old; and χ² = 21, p < 0.0001 for women 60–69 years old