Table 1. Comparison of clinical characteristics between breast cancer patients in the research group (≤34 years old) and the control group (35–49 years old).
| Epidemiological characteristics | ≤34 years old, *N (%) (n=295) | 35-49 years old, *N (%) (n=2,119) | ^P value |
|---|---|---|---|
| BMI, mean (range) | 21.09 (14.72–32.89) | 22.68 (14.87–38.52) | <0.001 |
| BMI subgroups | <0.001 | ||
| Underweight (≤18.49) | 24 (11.8) | 74 (4.4) | |
| Normal weight (18.50–24.99) | 160 (78.4) | 1,230 (73.5) | |
| Overweight and obese (≥25.00) | 20 (9.8) | 369 (22.1) | |
| Occupation | 0.005 | ||
| Manual worker | 118 (44.5) | 1,000 (54.2) | |
| Mental worker | 103 (38.9) | 548 (29.7) | |
| Others | 44 (16.6) | 297 (16.1) | |
| Education | <0.001 | ||
| Follow and primary school | 66 (41.8) | 606 (57.0) | |
| High school and above | 92 (58.2) | 458 (43.0) | |
| Age at first delivery (years) | 0.563 | ||
| ≤24 | 59 (44.0) | 439 (41.4) | |
| ≥25 | 75 (56.0) | 621(58.6) | |
| Number of live births | <0.001 | ||
| 0 | 24 (9.1) | 41(2.0) | |
| 1 | 192 (72.5) | 1,271 (63.3) | |
| ≥2 | 49 (18.5) | 696 (34.7) | |
| Breast feeding history | <0.001 | ||
| Yes | 147 (77.0) | 1,226 (90.2) | |
| No | 44 (23.0) | 133 (9.8) | |
| Breast cancer family history | 0.315 | ||
| No | 277 (95.2) | 2,000 (96.4) | |
| Yes | 14 (4.8) | 75 (3.6) | |
| Tumor location | 0.494 | ||
| Left | 158 (53.7) | 1,086 (51.6) | |
| Right | 136 (46.3) | 1,018 (48.4) | |
| Mass size | 0.617 | ||
| ≤20 mm | 76 (34.1) | 628 (35.8) | |
| ≥21 mm | 147 (65.9) | 1,127 (64.2) | |
| Local invasion | 0.178 | ||
| No | 228 (94.6) | 1,756 (96.4) | |
| Yes | 13 (5.4) | 66 (3.6) | |
| Postoperative pathological diagnosis | 0.531 | ||
| Carcinoma in situ | 15 (5.5) | 74 (3.7) | |
| breast cancer NOS | 232 (84.4) | 1,735 (86.1) | |
| Invasive lobular carcinoma | 9 (3.3) | 74 (3.7) | |
| Others | 19 (6.9) | 133 (6.6) | |
| Lymph node | 0.002 | ||
| No | 11 (42.6) | 1,037 (52.4) | |
| Yes | 155 (57.4) | 941 (47.6) | |
| ER status | 0.438 | ||
| ER+ | 129 (54.9) | 1,017 (57.6) | |
| ER− | 106 (45.1) | 750 (42.4) | |
| PR status | 0.033 | ||
| PR+ | 131 (55.7) | 1,112 (62.9) | |
| PR− | 104 (44.3) | 655 (37.1) | |
| HER-2 status | 0.927 | ||
| HER-2+ | 44 (21.5) | 349 (21.7) | |
| HER-2− (including both negative and uncertain) | 161 (78.5) | 1,256 (78.3) | |
| TNBC | 0.099 | ||
| No | 149 (72.7) | 1,348 (77.8) | |
| Yes | 56 (27.3) | 385 (22.2) | |
| TNM staging | 0.004 | ||
| I | 33 (15.2) | 349 (20.4) | |
| II | 108 (49.8) | 939 (54.8) | |
| III & IV | 76 (35.0) | 426 (24.9) |
*, or specified; ^, Chi-square test. Missing data in some of the following categories. NOS, not otherwise specified; BMI, body mass index; N, patient number of each subgroup; n, sampling size; ER estrogen receptor; PR progestogen receptor; TNBC triple negative breast cancer; HER-2, human epidermal growth factor receptor 2; TNM, tumor size, lymph nodes, and metastases.