Table 2.
Numbers of family members of the proband, number of observed cancer cases and standardized incidence ratios (SIR) for concordant cancers in family members by relatedness to the proband, when also the family member was diagnosed at ≤40 years
| Relatedness to the proband | Number of family members of the proband1 | Number of cancers2 | Person‐years | SIR for family member for concordant cancer3 | (95% CI) |
|---|---|---|---|---|---|
| Brain and other CNS cancers4 | |||||
| First‐degree relatives5 | 25,861 | 54 | 465,429 | 2.50 | (1.88–3.27) |
| Offspring | 5,829 | 23 | 126,523 | 3.66 | (2.32–5.49) |
| Father | 4,557 | 3 | 66,803 | 1.25 | (0.26–3.66) |
| Mother | 4,823 | 4 | 71,796 | 1.50 | (0.41–3.84) |
| Sibling | 10,652 | 24 | 200,307 | 2.35 | (1.50–3.49) |
| Sibling's offspring | 14,439 | 25 | 278,142 | 1.86 | (1.21–2.75) |
| Spouse | 9,833 | 6 | 191,816 | 0.60 | (0.22–1.31) |
| Breast cancer4 | |||||
| First degree relatives5 | 27,107 | 83 | 481,064 | 3.67 | (2.92–4.55) |
| Offspring | 9,443 | 32 | 214,269 | 3.61 | (2.47–5.10) |
| Father | 3,943 | 0 | 53,294 | 0.00 | (0.00–314) |
| Mother | 4,228 | 8 | 60,433 | 1.67 | (0.72–3.30) |
| Sibling | 9,493 | 43 | 153,068 | 4.80 | (3.47–6.47) |
| Sibling's offspring | 16,098 | 14 | 315,018 | 1.44 | (0.79–2.42) |
| Spouse | 12,202 | 3 | 196,073 | 0.33 | (0.07–0.97) |
| Colorectal cancer4 | |||||
| First degree relatives5 | 10,117 | 42 | 181,717 | 14 | (9.72‐18) |
| Offspring | 3,227 | 16 | 71,764 | 13 | (7.20–21) |
| Father | 1,520 | 6 | 21,369 | 20 | (7.21–43) |
| Mother | 1,615 | 4 | 22,946 | 14 | (3.72–35) |
| Sibling | 3,755 | 16 | 65,638 | 13 | (7.34–21) |
| Sibling's offspring | 6,228 | 4 | 122,967 | 1.97 | (0.54–5.06) |
| Spouse | 4,364 | 0 | 78,505 | 0.00 | (0.00–2.43) |
| Melanoma4 | |||||
| First degree relatives5 | 15,399 | 14 | 265,724 | 1.93 | (1.05–3.23) |
| Offspring | 4,875 | 6 | 103,170 | 1.98 | (0.73–4.31) |
| Father | 2,520 | 1 | 36,247 | 2.29 | (0.06–13) |
| Mother | 2,666 | 0 | 38,673 | 0.00 | (0.00–6.78) |
| Sibling | 5,338 | 7 | 87,634 | 2.15 | (0.86–4.43) |
| Sibling's offspring | 8,415 | 7 | 163,088 | 1.50 | (0.60–3.10) |
| Spouse | 6,338 | 5 | 107,597 | 1.25 | (0.41–2.92) |
1
Includes all family members.
2
Includes early‐onset cancers in family members of the proband.
3
SIR (95% CI) for concordant cancer in the family member of the proband.
4
p‐Value for homogeneity of the SIRs between first‐degree relatives combined and spouses was p < 0.001 for cancers of the CNS, breast and colorectum, and p = 0.39 for skin melanoma.
5
Includes offspring, father, mother and siblings of the proband.