Hormone replacement therapy and false positive recall in the Million Women Study: patterns of use, hormonal constituents and consistency of effect

Table 1 Breast cancer screening outcome in postmenopausal women for users of HRT compared to never users

	Total women screened (n = 87967^a)	Women recalled to assessment				Adjusted RR (95% CI) of false positive recall^b	Heterogeneity/trend, p-value
		No breast cancer (false positive recall)		Screen-detected breast cancer
		%	n	%	n
Total	87,967	3.0	2,629	0.5	399
Never used HRT^c	44,620	2.4	1,057	0.4	193	1.00	χ² ₁ (heterogeneity) = 90.1,
Ever used HRT	43,332	3.6	1,572	0.5	206	1.47 (1.36–1.60)	P < 0.001
Past user of HRT	13,829	2.8	382	0.3	48	1.21 (1.06–1.38)
Time since last use (median)							χ² ₁ (trend) = 14.0, p < 0.001
Current user (0 years)	28,788	4.0	1,157	0.5	154	1.64 (1.50–1.80)
<1 year since last use (0.5 years)	1,764	3.6	63	0.3	6	1.42 (1.08–1.86)
1–4 years since last use (2 years)	5,931	3.0	176	0.4	21	1.23 (1.04–1.46)
≥5 years since last use (7 years)	3,813	2.4	92	0.3	13	1.07 (0.85–1.34)
Duration of use among current users of HRT (median)							χ² ₁ (trend) = 2.1, p = 0.2
<1 year (0.5 years)	1,935	3.9	75	0.3	5	1.41 (1.10–1.81)
1–4 years (3 years)	9,790	4.2	410	0.6	54	1.58 (1.40–1.79)
5–9 years (6 years)	11,280	3.9	441	0.6	71	1.74 (1.53–1.97)
≥10 years (11 years)	4,963	3.9	193	0.4	21	1.74 (1.46–2.06)
Duration of use among past users of HRT (median)							χ² ₁ (trend) = 8.4, p = 0.004
<1 year (0.5 years)	4,014	2.4	95	0.3	13	0.95 (0.77–1.18)
1–4 years (3 years)	5,152	2.8	143	0.3	17	1.29 (1.07–1.56)
≥5 years (8 years)	3,061	3.4	104	0.5	14	1.54 (1.23–1.93)

^aNumbers do not always add up to total due to missing values. ^bStratified by screening centre, age, time since menopause, previous screening, body mass index and previous breast operation. ^cReference group. CI, confidence interval; HRT, hormone replacement therapy; RR, relative risk.

ISSN: 1465-542X