Table 1 Characteristics of study participants
Screen-detected cases | Interval cases | ||||||
|---|---|---|---|---|---|---|---|
Cases (n = 244) | Controls (n = 700) | P | Cases (n = 148) | Controls (n = 446) | P | P a | |
Age at baseline, years | 56 (8) | 56 (8) | 0.72 | 54 (8) | 54 (8) | 0.72 | 0.01 |
Age at mammogram, years | 59 (7) | 59 (7) | 0.82 | 57 (7) | 57 (7) | 0.79 | <0.01 |
Age at diagnosis, years | 65 (7) | 62 (7) | <0.001 | ||||
Time between age at mammogram and reference age, years | 6 (3) | 6 (3) | 0.58 | 5 (3) | 5 (4) | 0.93 | 0.12 |
Total energy intake, MJ/day | 8.4 (2.9) | 8.6 (3.5) | 0.40 | 8.7 (3.2) | 8.7 (3.1) | 0.91 | 0.30 |
BMI, kg/m2 | |||||||
All women | 27.5 (4.9) | 26.7 (4.9) | 0.04 | 26.7 (5.3) | 26.5 (4.8) | 0.68 | 0.11 |
Premenopausal | 27.2 (5.7) | 26.2 (5.0) | 0.17 | 25.9 (4.9) | 26.1 (4.6) | 0.72 | 0.15 |
Postmenopausal | 27.6 (4.6) | 27.0 (4.9) | 0.10 | 27.2 (5.5) | 26.7 (5.0) | 0.41 | 0.51 |
BMI at age 18–21 years, kg/m2 | 21.5 (2.9) | 21.5 (2.9) | 0.86 | 21.4 (2.5) | 21.5 (2.8) | 0.54 | 0.66 |
Breast | |||||||
Total area, cm2 | 143.7 (60.9) | 137.8 (57.6) | 0.17 | 125.0 (56.9) | 133.4 (60.3) | 0.14 | <0.01 |
Non-dense area, cm2 | 124.2 (62.1) | 120.9 (58.8) | 0.47 | 96.5 (55.6) | 115.3 (60.6) | <0.001 | <0.0001 |
Dense area, cm2 | 19.6 (21.7) | 16.8 (20.6) | 0.08 | 28.5 (24.5) | 18.1 (19.4) | <0.0001 | <0.001 |
Percent dense area | 15.5 (15.7) | 14.0 (15.3) | 0.18 | 25.2 (17.9) | 15.4 (14.7) | <0.0001 | <0.0001 |
Country of birth, n (%) | |||||||
Anglo Saxon/other | 204 (84) | 583 (83) | 0.99 | 123 (83) | 371 (83) | 0.99 | 0.70 |
Italy | 25 (10) | 74 (11) | 13 (9) | 40 (9) | |||
Greece | 15 (6) | 43 (6) | 12 (8) | 35 (8) | |||
Age at menarche, years n (%) | |||||||
<12 | 47 (19) | 125 (18) | 0.92 | 31 (21) | 75 (17) | 0.69 | 0.74 |
12 | 52 (21) | 145 (21) | 25 (17) | 86 (19) | |||
13 | 55 (23) | 169 (24) | 36 (24) | 111 (25) | |||
14+ | 88 (36) | 261 (37) | 56 (38) | 174 (39) | |||
Parity and lactation, n (%), | |||||||
Nulliparous | 38 (16) | 84 (12) | 0.03 | 25 (17) | 62 (14) | 0.63 | 0.22 |
Parous, never lactated | 10 (4) | 61 (9) | 12 (8) | 34 (8) | |||
Parous, lactated | 190 (78) | 542 (77) | 108 (73) | 343 (77) | |||
Menopausal status n (%) | |||||||
Premenopausal | 69 (28) | 195 (28) | 0.88 | 59 (40) | 170 (38) | 0.72 | 0.02 |
Postmenopausal | 174 (71) | 504 (72) | 89 (60) | 275 (62) | |||
Hormone replacement therapy use, n (%) | |||||||
Never | 169 (69) | 493 (70) | 0.75 | 98 (66) | 323 (72) | 0.17 | 0.55 |
Ever | 74 (30) | 205 (29) | 49 (33) | 122 (27) | |||
Oral contraceptive use, n (%) | |||||||
Never | 93 (38) | 283 (40) | 0.53 | 58 (39) | 157 (35) | 0.4 | 0.86 |
Ever | 150 (61) | 415 (59) | 90 (61) | 287 (64) | |||
Alcohol consumption, n (%) | |||||||
Lifetime abstainers | 109 (45) | 257 (37) | 0.10 | 43 (29) | 160 (36) | 0.3 | <0.01 |
Ex-drinkers | 13 (5) | 24 (3) | 3 (2) | 13 (3) | |||
Low intake, 1–19 g/day | 97 (40) | 337 (48) | 78 (53) | 223 (50) | |||
Medium intake, 20–39 g/day | 19 (8) | 61 (9) | 20 (14) | 38 (9) | |||
High intake, ≥40 g/day | 6 (2) | 21 (3) | 4 (3) | 12 (3) | |||
Family history of breast cancerb, n (%) | |||||||
No | 185 (76) | 548 (78) | 0.08 | 101 (68) | 341 (76) | <0.001 | 0.18 |
Yes | 38 (16) | 77 (11) | 30 (20) | 43 (10) | |||
ER, n (%) | |||||||
Positive | 188 (77.0) | 94 (63.5) | <0.01 | ||||
Negative | 45 (18.4) | 45 (30.4) | |||||
PR, n (%) | |||||||
Positive | 126 (51.6) | 57 (38.5) | 0.02 | ||||
Negative | 106 (43.4) | 80 (54.1) | |||||
HER2, n (%) | |||||||
Positive | 73 (29.9) | 41 (27.7) | 0.64 | ||||
Negative | 153 (62.7) | 96 (64.9) | |||||
Grade n (%) | |||||||
Well-differentiated | 62 (25.4) | 24 (16.2) | <0.01 | ||||
Moderately differentiated | 104 (42.6) | 52 (35.1) | |||||
Poorly differentiated | 65 (26.6) | 61 (41.2) | |||||
Nodal status, n (%) | |||||||
Positive | 39 (16.0) | 65 (43.9) | <0.001 | ||||
Negative | 190 (77.9) | 71 (48.0) | |||||
Tumor size, n (%) | |||||||
<1 cm | 76 (31.1) | 25 (16.9) | <0.001 | ||||
1–2 cm | 116 (47.5) | 51 (34.5) | |||||
≥2 cm | 49 (20.1) | 65 (43.9) | |||||