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Table 2

Change in mammographic features after treatment with tamoxifen or placebo

	Percentage of women changing to a parenchymal pattern of lower radiologic density					Mean reduction in the estimated percentage of the breast showing radiological densities
		Tamoxifen % (n^a)	Placebo % (n)	P ^b	Tamoxifen Mean ± SD (n)	Placebo Mean ± SD (n)	P ^b
All women	44.4 (36)	15.2 (33)	0.010	−9.4 ± 12.0 (36)	−3.6 ± 5.3 (33)	0.010^c
Age at baseline (yr)
<50	66.7 (21)	18.8 (16)	0.007	−12.1 ± 11.0 (21)	−3.6 ± 4.5 (16)	0.003^c
≥50	13.3 (15)	11.8 (17)	1	−5.7 ± 12.6 (15)	−3.5 ± 6.2 (17)	0.540^d
Duration of treatment (yr)
1.0–3.4	38.5 (13)	6.7 (15)	0.069	−6.9 ± 11.1 (13)	−3.3 ± 3.5 (15)	0.282^c
3.5–5.0	47.8 (23)	22.2 (18)	0.114	−10.9 ± 12.4 (23)	−3.8 ± 6.6 (18)	0.024^c

	Percentage of women changing to a parenchymal pattern of lower radiologic density					Mean reduction in the estimated percentage of the breast showing radiological densities
		Tamoxifen % (n^a)	Placebo % (n)	P ^b	Tamoxifen Mean ± SD (n)	Placebo Mean ± SD (n)	P ^b
All women	44.4 (36)	15.2 (33)	0.010	−9.4 ± 12.0 (36)	−3.6 ± 5.3 (33)	0.010^c
Age at baseline (yr)
<50	66.7 (21)	18.8 (16)	0.007	−12.1 ± 11.0 (21)	−3.6 ± 4.5 (16)	0.003^c
≥50	13.3 (15)	11.8 (17)	1	−5.7 ± 12.6 (15)	−3.5 ± 6.2 (17)	0.540^d
Duration of treatment (yr)
1.0–3.4	38.5 (13)	6.7 (15)	0.069	−6.9 ± 11.1 (13)	−3.3 ± 3.5 (15)	0.282^c
3.5–5.0	47.8 (23)	22.2 (18)	0.114	−10.9 ± 12.4 (23)	−3.8 ± 6.6 (18)	0.024^c

^a

Total number of women in category.

^b

Fisher’s exact test. All Ps are two-sided.

^c

t test with unequal variances.

^d

t test with equal variances.