Table 1. Characteristics of a cohort of postmenopausal Swedish women with a breast cancer diagnosis between 1961 and 2003, and SIR, with 95% CI, of oesophageal adenocarcinoma.

	Oesophageal adenocarcinoma
	Unexposed (1961–1987)	Exposed (1988–2003)	Total cohort (1961–2003)
No. of breast cancer cases	73 377	65 508	138 885
No. of person-years at risk	711 837	363 887	1 075 724
Mean years of follow-up	9.70	5.55	7.74
Mean age at entry (range)	68 (50–101)	68 (50–104)	68 (50–104)
No. of observed oesophageal adeno-carcinoma cases	10	9	19
No. of expected oesophageal adeno-carcinoma cases	8.49	5.61	14.10
SIR (95% CI)	1.17 (0.63–2.18)	1.60 (0.83–3.08)	1.34 (0.85–2.11)
Latency interval after breast cancer diagnosis in years	Number of observed cases of oesophageal adenocarcinoma SIR (95% CI)
1–4	1	5	6
	0.61 (0.08–4.36)	1.85 (0.77–4.44)	1.38 (0.62–3.08)
5–9	3	3	6
	1.68 (0.54–5.22)	1.44 (0.46–4.47)	1.55 (0.69–3.46)
10–14	3	1	4
	1.67 (0.54–5.20)	1.23 (0.17–8.74)	1.53 (0.57–4.10)
>15	3	0	3
	0.90 (0.29–2.81)		0.90 (0.29–2.80)

CI=confidence interval; SIR=standardised incidence ratio.

Patients diagnosed with breast cancer between 1961 and 1987 were considered unexposed to tamoxifen treatment, whereas those diagnosed between 1988 and 2003 were considered exposed. First year of follow-up was excluded.