Risk of invasive breast cancer in relatives of patients with breast carcinoma in situ: a prospective cohort study

Table 2 Relative risk of breast cancer by age at diagnosis in sisters and mothers

Age at diagnosis in index woman (years)	Age at diagnosis in relative (years)	Affected first-degree relative
		Sister						Mother
		In situ			Invasive			In situ			Invasive
		Obs	SIR	95% CI	Obs	95% CI		Obs	SIR	95% CI	Obs	SIR	95% CI
All ages	All ages	251	1.5	1.4–1.7	2962	1.8	1.7–1.9	266	1.5	1.3–1.7	8456	1.8	1.7–1.8
	< 50	92	1.7	1.4–2.1	1135	1.9	1.8–2.0	22	1.3	0.8–2.0	1175	2.2	2.1–2.3
	≥ 50	159	1.5	1.2–1.7	1827	1.7	1.7–1.8	244	1.5	1.3–1.7	7281	1.7	1.7–1.8
< 50	All ages	32	2.2	1.5–3.1	356	2.4	2.2–2.7	93	1.4	1.1–1.7	2490	2.0	2.0–2.1
	< 50	21	2.1	1.3–3.2	265	2.4	2.1–2.7	9	1.0	0.5–1.9	625	2.8	2.6–3.0
	≥ 50	11	2.6	1.3–4.6	91	2.5	2.0–3.1	84	1.5	1.2–1.8	1865	1.9	1.8–2.0
≥ 50	All ages	219	1.5	1.3–1.7	2606	1.8	1.7–1.8	173	1.5	1.3–1.8	5966	1.7	1.6–1.7
	< 50	71	1.6^§	1.3–2.0	870	1.8^§	1.7–2.0	13	1.7^§	0.9–2.9	550	1.8^§	1.7–2.0
	≥ 50	148	1.4	1.2–1.7	1736	1.7	1.6–1.8	160	1.5	1.3–1.8	5416	1.7	1.6–1.7

Notes: The reference group included women with no family history of both in situ and invasive breast cancer in first- and second-degree relatives. All SIRs were adjusted for age, sex, socio-economic status, period, and region. Bold SIRs are statistically significant
Obs observed number of breast cancer cases, SIR standardized incidence ratio, CI confidence interval
^§Example: For women older than 50 years, having one sister or a mother diagnosed with breast carcinoma in situ after age 50 years was associated with 60% and 70%, respectively, both of which were comparable to risk associated with either relative diagnosed before age 50 years with invasive breast cancer

ISSN: 1741-7015