Table 2.

Odds ratios (95% confidence interval) of developing subsequent breast cancer according to tertiles of mean percentage of p27⁺, ER⁺, and Ki67⁺ in normal breast tissue in the Nurses’ Health Study and the Nurses’ Health Study II.

	Case	Control	Model 1^a OR (95% CI)	Model 2^b OR (95% CI)
Percentage of p27⁺ cells
< 8.0 %	25	75	1.0 (Ref)	1.0 (Ref)
8.0 – 25.4 %	21	78	0.73 (0.37, 1.46)	0.86 (0.42, 1.76)
≥ 25.5 %	23	78	0.84 (0.43, 1.63)	0.89 (0.45, 1.75)
Per 1% increase			1.00 (0.98, 1.02)	1.00 (0.99, 1.02)
p-trend			0.99	0.97
Percentage of ER⁺ cells
< 3.0 %	24	72	1.0 (Ref)	1.0 (Ref)
3.0 – 9.9 %	22	71	0.98 (0.49, 1.94)	0.90 (0.45, 1.80)
≥ 10.0 %	19	76	0.86 (0.42, 1.77)	0.70 (0.33, 1.50)
Per 1% increase			1.00 (0.98, 1.03)	1.00 (0.97, 1.02)
p-trend			0.86	0.84
Percentage of Ki67⁺ cells
< 0.28 %	13	64	1.0 (Ref)	1.0 (Ref)
0.28 – 2.0 %	18	60	1.66 (0.72, 3.85)	1.63 (0.70, 3.80)
≥ 2.0 %	21	55	1.94 (0.85, 4.44)	1.92 (0.83, 4.43)
Per 1% increase			1.05 (0.98, 1.13)	1.05 (0.98, 1.13)
p-trend			0.15	0.14
Percentage of p27⁺ER⁺ cells
< 1.5 %	22	72	1.0 (Ref)	1.0 (Ref)
1.5 – 5.4 %	26	68	1.33 (0.67, 2.61)	1.23 (0.62, 2.45)
≥ 5.5 %	17	79	0.77 (0.37, 1.60)	0.69 (0.33, 1.46)
Per 1% increase			1.00 (0.96, 1.04)	1.00 (0.96, 1.04)
p-trend			0.91	0.97
Percentage of p27⁺Ki67⁺ cells
< 0.16 %	22	82	1.0 (Ref)	1.0 (Ref)
0.16 – 1.4 %	11	40	1.11 (0.47, 2.61)	1.24 (0.52, 2.96)
≥ 1.5 %	19	57	1.29 (0.61, 2.71)	1.36 (0.64, 2.90)
Per 1% increase			1.03 (0.86, 1.22)	1.05 (0.88, 1.25)
p-trend			0.76	0.62

Model 1 (Matching factors only): age at diagnosis (continuous, years), calendar year of biopsy (<1970, 1970–1980, 1980+), time since biopsy (continuous, years).

Model 2: Model 1 + type of benign lesion (nonproliferative, proliferative without atypia, proliferative with atypia).