Table 3 Familial cancer risks for people with multiple affected relatives.

Case numbers ¹ , Relative risk, 95%CI

Both parents affected

63

25

11

0

6

8

3

1.98 (1.46–2.69)

3.02 (1.86–4.92)

9.49 (4.58–19.67)

3.50 (0.92–13.28)

6.00 (2.54–14.15)

3.64 (0.82–16.17)

1 parent and 1 sibling affected

186

42

485

930

12

50

24

3.67 (3.07–4.39)

2.48 (1.70–3.61)

2.88 (2.58–3.21)

4.59 (4.23–4.98)

2.86 (1.11–7.35)

8.20 (5.81–11.56)

9.47 (5.59–16.05)

2 siblings affected

33

27

199

368

3

15

0

2.57 (1.68–3.91)

3.39 (2.12–5.42)

2.50 (2.11–2.97)

5.25 (4.62–5.98)

2.74 (0.42–18.03)

4.47 (2.39–8.37)

3 siblings affected

4

4

4

44

0

0

0

6.59 (1.97–22.08)

20.84 (6.17–70.38)

1.02 (0.30–3.41)

6.78 (4.68–9.83)

P-values for differences among RRs ²

Both parents vs. 1 parent

0.36

0.0528

<.0001

0.31

0.0398

0.26

1 Parent and 1 sibling vs. 1 parent

<.0001

0.14

<.0001

<.0001

0.32

<.0001

<.0001

1 Parent and 1 sibling vs. 1 sibling

<.0001

0.95

<.0001

<.0001

0.41

<.0001

<.0001

2 siblings vs. 1 sibling

0.25

0.22

0.0006

<.0001

0.71

0.13

3 siblings vs. 1 sibling

0.0528

0.0007

0.34

<.0001

3 siblings vs. 2 sibling

0.15

0.0063

0.15

0.20

1 Parent and 1 sibling vs. 2 siblings

0.12

0.31

0.18

0.08

0.97

0.10

1 Parent and 1 sibling vs. both parents

0.0006

0.53

0.0015

0.81

0.51

0.24

2 siblings vs. both parents

0.33

0.74

0.0005

0.83

0.59