Table 3.
Numbers of family members of the proband, number of observed cancer cases and standardized incidence ratios (SIR) for early‐onset (≤40 years) concordant cancer in siblings of the proband by concordant parental cancer at any age
| Relatedness to the proband | Number of family members of the proband | Number of cancers | Person‐years | SIR for concordant cancer1 | (95% CI) |
|---|---|---|---|---|---|
| Brain and other CNS cancers2 | |||||
| Sibling with affected parent3 | 194 | 6 | 3,954 | 29 | (11–64) |
| Sibling without affected parent4 | 10,458 | 18 | 196,353 | 1.80 | (1.06–2.84) |
| Breast cancer2 | |||||
| Sibling with affected parent3 | 980 | 10 | 15,226 | 10 | (4.85–19) |
| Sibling without affected parent4 | 8,513 | 33 | 137,842 | 4.14 | (2.85–5.81) |
| Colorectal cancer2 | |||||
| Sibling with affected parent3 | 363 | 10 | 6,405 | 905 | (43–165) |
| Sibling without affected parent4 | 3,392 | 6 | 59,233 | 5.29 | (1.94–12) |
| Melanoma2 | |||||
| Sibling with affected parent3 | 193 | 0 | 3,414 | 0.00 | (0.00–30) |
| Sibling without affected parent4 | 5,145 | 7 | 84,220 | 2.23 | (0.90–4.60) |
SIR (95% CI) for concordant cancer in the family member of the proband.
According to pathological reports retrieved from the Finnish Cancer Registry for siblings with affected parents, all brain and CNS cases were in families with neurofibromatosis in at least one subjects with diagnosed cancer. We found no record of BRCA carriers among breast cancer probands and their siblings or parents. FAP or HNPCC was found in four of the 10 multiplex colorectal cancer families.
At least one sibling diagnosed with the concordant cancer at age ≤40 years and at least either one of the parents diagnosed with the concordant cancer at any age. There were no families with both affected parents.
At least one sibling diagnosed with the concordant cancer at age ≤40 years, no parents with concordant cancer.
SIR for the families without FAP or HNPCC was 56 (21–122).