Table 1.
Descriptive statistics comparing screen-detected cancers and interval cancers
| Characteristics | Screen-detected cancers (n = 1,115) | Interval cancers (n = 285) | P value |
|---|---|---|---|
| Mean age at mammography (yr) | 62.0 | 60.9 | 0.012 |
| Mean BMI | 26.1 | 25.2 | <0.001 |
| Mean age at menarche (yr) | 13.5 | 13.5 | 0.442 |
| Oral contraceptive use, n (%) | 0.003 | ||
| Yes | 358 (32%) | 118 (42%) | |
| No | 754 (68%) | 165 (58%) | |
| Mean age at first birth (yr) | 25.4 | 25.0 | 0.172 |
| Mean parity (n) | 1.8 | 1.9 | 0.775 |
| Breastfeeding, n (%) | 0.152 | ||
| Yes | 777 (78%) | 211 (82%) | |
| No | 219 (22%) | 46 (18%) | |
| Mean age at menopause (yr) | 50.4 | 50.2 | 0.302 |
| HRT use, n (%) | <0.001 | ||
| Never | 800 (73%) | 160 (57%) | |
| Past | 247 (22%) | 71 (25%) | |
| Current | 54 (5%) | 52 (18%) | |
| Previous benign breast disease, n (%) | 0.182 | ||
| Yes | 146 (13%) | 46 (16%) | |
| No | 965 (87%) | 238 (84%) | |
| Breast cancer hereditya, n (%) | 0.434 | ||
| Yes | 160 (15%) | 46 (17%) | |
| No | 923 (85%) | 230 (83%) | |
| Percentage density (PD), n (%) | <0.001 | ||
| <5% | 240 (22%) | 38 (13%) | |
| 5% to <10% | 207 (19%) | 50 (18%) | |
| 10% to <25% | 420 (38%) | 100 (35%) | |
| 25% to <50% | 214 (19%) | 79 (28%) | |
| ≥50% | 34 (3%) | 18 (6%) | |
aFamily history of breast cancer in a first-degree relative. BMI, body mass index; HRT, hormone replacement therapy.