Table 1.

Observed breast cancers in total series and subgroups based on family history in woman <50 years, in women 50–59 years, and in total series compared to expected compared to population

Groups (Number in group)	Ages	Observation years	Observed breast cancers	Expected breast cancers	χ 2
Total series (n = 3,161)	25–49	17,873	36	16.8	21.9**
	50–59	6,935	28	17.2	6.8**
	25–59	24,808	64	34.0	26.4**
Four breast cancer cases or more in family (n = 314)	25–49	1,626	5	1.6	7.2**
	50–59	836	4	2.1	1.8
	25–59	2,462	9	3.7	7.7**
Two breast cancer cases = <55 years or more in family (n = 865)	25–49	5,085	15	4.6	23.1**
	50–59	1,819	11	4.5	9.3**
	25–59	6,904	26	9.2	31.0**
One case only in family and that case = <50 years (n = 735)	25–49	4,669	6	4.2	0.8
	50–59	1,474	5	3.7	0.5
	25–59	6,143	11	7.8	1.3
Breast and ovarian cancer in family	25–49	4,370	7	4.1	2.0
	50–59	1,890	7	4.7	1.1
	25–59	6,260	14	8.7	3.1

(no result had 0.05<p<0.01), ** p < 0.01