Table 2. Characteristics of a cohort of postmenopausal Swedish women with a breast cancer diagnosis between 1970 and 2003, and SIR, with 95% CI, of gastric cardia adenocarcinoma.

	Gastric cardia adenocarcinoma
	Unexposed (1970–1987)	Exposed (1988–2003)	Total cohort (1970–2003)
No. of breast cancer cases	53 643	65 505	119 148
No. of person-years at risk	528 789	363 765	892 555
Mean years of follow-up	9.85	5.55	7.49
Mean age at entry (range)	69 (50–101)	68 (50–104)	68 (50–104)
No. of observed gastric cardia adenocarcinoma cases	12	9	21
No. of expected gastric cardia adeno-carcinoma cases	15.95	9.28	25.24
SIR (95% CI)	0.75 (0.42–1.32)	0.96 (0.5–1.86)	0.83 (0.54–1.27)
Latency interval after breast cancer diagnosis in years	Number of observed cases of gastric cardia adenocarcinoma SIR (95% CI)
1–4	3	5	8
	0.73 (0.23–2.28)	1.03 (0.43–2.48)	0.89 (0.44–1.79)
5–9	3	3	6
	0.68 (0.21–2.11)	0.93 (0.30–2.89)	0.78 (0.35–1.75)
10–14	3	1	4
	0.85 (0.27–2.65)	0.82 (0.11–5.86)	0.84 (0.31–2.26)
>15	3	0	3
	0.75 (0.24–2.33)		0.74 (0.24–2.32)

CI=confidence interval; SIR=standardised incidence ratio.

Patients diagnosed with breast cancer between 1970 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. The earliest data available for the gastric cancer diagnosis were from 1961, but distinction between cardia and non-cardia diagnoses was only available from 1970.