Table 2. SIRs for malignant breast tumours among women with a previous diagnosis of glandular cervical precancer.

	Woman-years	Observed number of cases	Expected number of cases	SIR (95% CI)	P -value
DCIS+	17 384	39	25.70	1.52 (1.11–2.08)	<0.01
Age at diagnosis of DCIS+
<20	1	0	0.00	NA	NA
20–29	1160	0	0.04	NA	NA
30–39	4993	1	1.75	0.57 (0.08–4.06)	0.58
40–49	4723	10	6.58	1.52 (0.82–2.82)	0.19
50–59	3362	14	8.46	1.66 (0.98–2.79)	0.06
60–69	1870	5	5.60	0.89 (0.37–2.14)	0.80
70–79	930	8	2.27	3.52 (1.76–7.04)	<0.01
80+	345	1	0.99	1.01 (0.14–7.15)	0.99
Period of diagnosis of DCIS+
1970–79	391	0	0.41	NA	NA
1980–89	1259	1	1.57	0.64 (0.09–4.53)	0.65
1990–99	4212	13	5.74	2.27 (1.32–3.90)	<0.01
2000–08	11 522	25	17.99	1.39 (0.94–2.06)	0.10
Localised tumoursa	17 455	21	13.96	1.50 (0.98–2.31)	0.06
Metastatic tumoursb	17 562	18	11.89	1.51 (0.95–2.40)	0.08

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.