Table 1. SIRs for malignant breast tumours among women with a previous diagnosis of squamous cervical precancer.

	Woman-years	Observed number of cases	Expected number of cases	SIR (95% CI)	P -value
DCIS+	1374461	2054	1873.65	1.10 (1.05–1.14)	<0.01
Age at diagnosis of DCIS+
<20	1362	0	0.00	NA	NA
20–29	119 671	5	3.76	1.33 (0.55–3.20)	0.52
30–39	389 931	150	133.88	1.12 (0.95–1.31)	0.16
40–49	406 093	602	545.08	1.10 (1.02–1.20)	0.01
50–59	269 067	719	659.27	1.09 (1.01–1.17)	0.02
60–69	124 534	402	369.45	1.09 (0.99–1.20)	0.09
70–79	50 218	139	122.93	1.13 (0.96–1.34)	0.15
80+	13 583	37	39.28	0.94 (0.68–1.30)	0.72
Period of diagnosis of DCIS+
1970–79	57 188	29	35.15	0.83 (0.57–1.19)	0.30
1980–89	226 645	193	174.42	1.11 (0.96–1.27)	0.16
1990–99	465 185	583	553.30	1.05 (0.97–1.14)	0.21
2000–08	625 443	1249	1110.78	1.12 (1.06–1.19)	<0.01
Localised tumoursa	1379352	1161	1016.44	1.14 (1.08–1.21)	<0.01
Metastatic tumoursb	1382705	879	858.79	1.02 (0.96–1.09)	0.49

Abbreviations: CI=confidence interval; DCIS+=ductal carcinoma in situ or invasive breast cancer; NA=not available; SIR=standardised incidence ratio.

^aLocalised tumours=DCIS and invasive breast cancer stage 1.

^bMetastatic tumours=invasive breast cancer stages 2–4.