Table 1 Distributions of demographic, lifestyle, and reproductive features of unilateral and bilateral breast cancer cases, at time of first diagnosis
Bilateral | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Unilateral ( N =1863) | Synchronous ( N =17) | Metachronous ( N =26) | Overall ( N =43) | |||||||
Variable | No. | % | No. | % | No. | % | No. | % | P -value a | P -value b |
Age(years)c | 49.8±12.2 (47.9) | 49.0±8.1 (46.1) | 48.5±11.2 (50.1) | 48.7±10.0 (49.5) | 0.85 | 0.95 | ||||
BMI | 23.4±3.6 | 22.8±4.1 | 22.4±2.9 | 22.6±3.4 | 0.34 | 0.83 | ||||
Education (%) | 0.68 | 0.48 | ||||||||
College or above | 382 | 27.3 | 4 | 33.3 | 3 | 21.4 | 7 | 26.9 | ||
Senior high school | 340 | 24.3 | 3 | 25.0 | 1 | 7.1 | 4 | 15.4 | ||
Junior high school | 181 | 12.9 | 1 | 8.3 | 4 | 28.6 | 5 | 19.2 | ||
Elementary school | 351 | 25.1 | 3 | 25.0 | 3 | 21.4 | 6 | 23.1 | ||
Illiterate | 144 | 10.3 | 1 | 8.3 | 3 | 21.4 | 4 | 15.4 | ||
Age at menarche | 14.4±1.7 | 14.1±1.6 | 14.6±1.8 | 14.4±1.7 | 0.91 | 0.29 | ||||
Menopause | 0.07 | 0.70 | ||||||||
Yes | 739 | 55.8 | 8 | 66.7 | 15 | 75.0 | 23 | 71.9 | ||
No | 585 | 44.2 | 4 | 33.3 | 5 | 25.0 | 9 | 28.1 | ||
Age of menopause | 48.4±5.3 | 49.3±4.9 | 48.3±6.4 | 48.7±5.9 | 0.69 | 0.52 | ||||
Hysterectomy | 0.78 | 1.00 | ||||||||
Yes | 146 | 8.4 | 1 | 5.9 | 3 | 11.5 | 4 | 9.3 | ||
No | 1585 | 91.6 | 16 | 94.1 | 23 | 88.5 | 39 | 90.7 | ||
Pregnancy | 3.3±2.2 | 2.5±1.3 | 3.0±2.2 | 2.8±1.8 | 0.26 | 0.49 | ||||
Childbirth | 2.6±1.7 | 2.1±1.2 | 2.4±1.6 | 2.2±1.4 | 0.41 | 0.48 | ||||
Miscarriage | 0.7±1.1 | 0.4±0.6 | 0.6±1.1 | 0.5±0.9 | 0.33 | 0.91 | ||||
Age of first childbirth | 25.5±4.6 | 23.5±3.9 | 25.9±5.6 | 25.0±5.0 | 0.41 | 0.34 | ||||
Breast feeding | 0.15 | 0.34 | ||||||||
Yes | 420 | 60.8 | 1 | 20.0 | 7 | 50.0 | 8 | 42.1 | ||
No | 271 | 39.2 | 4 | 80.0 | 7 | 50.0 | 11 | 57.9 | ||
Smoking | 1.00 | 1.00 | ||||||||
Yes | 47 | 2.6 | 0 | 0.0 | 1 | 4.2 | 1 | 2.6 | ||
No | 1739 | 97.4 | 15 | 100.0 | 23 | 95.8 | 38 | 97.4 | ||
Drinking | 0.65 | 0.14 | ||||||||
Yes | 65 | 3.6 | 2 | 13.3 | 0 | 0.0 | 2 | 5.1 | ||
No | 1722 | 96.4 | 13 | 86.7 | 24 | 100.0 | 37 | 94.9 | ||
Family history of breast cancer | 0.05 | 1.00 | ||||||||
Yes | 86 | 4.6 | 2 | 11.8 | 3 | 11.5 | 5 | 11.6 | ||
No | 1777 | 95.4 | 15 | 88.2 | 23 | 88.5 | 38 | 88.4 | ||
