Table 2. Characteristics of young-onset breast cancer families included in the genotyping analysis, as defined by the affected sistera: Two Sister Study (n=1242 cases; 2008–2010) and Sister Study (n=235 cases; 2003–2009).
| N (%) | |
|---|---|
| Age at diagnosis | |
| <40 | 161 (11) |
| 40–49 | 1315 (89) |
| Missing | 1 |
| Race/ethnicity | |
| Non-Hispanic white | 1296 (88) |
| Hispanic | 54 (4) |
| African-American | 85 (6) |
| Other | 40 (3) |
| Missing | 2 |
| Menopausal status at diagnosis | |
| Premenopausal (with or without hysterectomy) | 1359 (93) |
| Postmenopausal | 100 (7) |
| Missing | 18 |
| Invasive status | |
| Ductal carcinoma in situ | 239 (17) |
| Invasive | 1208 (83) |
| Missing | 30 |
| Estrogen receptor status | |
| Positive | 1146 (80) |
| Negative | 282 (20) |
| Missing | 49 |
| BRCA1/2 statusb | |
| Case carries BRCA1/2 mutation | 116 (8) |
| Case not known to have BRCA1/2 mutation | 1361 (92) |
a
This includes 29 families where the affected sister was not included in the genotype analysis, but other members of the family were.
b
Families were categorized as BRCA1 or BRCA2 mutation positive if (1) the case sister reported that she had had a positive test or (2) the case sister was not tested but the unaffected sister reported that she had had a positive test.