Table 1. Characteristics of patients by tumor laterality.
| Characteristic | All patients (n = 4,333) No. (%) |
Right-sided (n = 2,256) No. (%) |
Left-sided (n = 2,077) No. (%) |
p-value |
|---|---|---|---|---|
| Year of RT | 0.434 | |||
| 1996–2000 | 367 (8.5) | 202 (9.0) | 165 (7.9) | |
| 2001–2005 | 1,333 (30.8) | 683 (30.3) | 650 (31.3) | |
| 2006–2010 | 2,633 (60.8) | 1,371 (60.8) | 1,262 (60.8) | |
| Age (yr) | 0.981 | |||
| < 40 | 733 (16.9) | 379 (16.8) | 354 (17.0) | |
| 40–49 | 1,900 (43.8) | 996 (44.1) | 904 (43.5) | |
| 50–59 | 1,199 (27.7) | 622 (27.6) | 577 (27.8) | |
| ≥ 60 | 501 (11.6) | 259 (11.5) | 242 (11.7) | |
| BMI (kg/m2) | 0.567 | |||
| Unknown | 439 (10.1) | 218 (9.7) | 221 (10.6) | |
| < 25 | 2,795 (64.5) | 1,463 (64.8) | 1,332 (64.1) | |
| ≥ 25 | 1,099 (25.4) | 575 (25.5) | 524 (25.2) | |
| Smoking | 0.247 | |||
| Unknown | 856 (19.8) | 454 (20.1) | 402 (19.4) | |
| Yes | 92 (2.1) | 55 (2.4) | 37 (1.8) | |
| No | 3,385 (78.1) | 1,747 (77.4) | 1,638 (78.9) | |
| Hyperlipidemia | 0.465 | |||
| Yes | 335 (7.7) | 168 (7.4) | 167 (8.0) | |
| No | 3,998 (92.3) | 2,088 (92.6) | 1,910 (92.0) | |
| Hypertension | 0.257 | |||
| Yes | 254 (5.9) | 141 (6.3) | 113 (5.4) | |
| No | 4,079 (94.1) | 2,115 (93.8) | 1,964 (94.6) | |
| Diabetes | 0.845 | |||
| Yes | 201 (4.6) | 106 (4.7) | 95 (4.6) | |
| No | 4,132 (95.4) | 2,150 (95.3) | 1,982 (95.4) | |
| pT stage | 0.643 | |||
| Tis | 510 (11.8) | 264 (11.7) | 246 (11.8) | |
| T1 | 2,571 (59.3) | 1,327 (58.8) | 1,244 (59.9) | |
| T2 | 1,158 (26.7) | 609 (27.0) | 549 (26.4) | |
| T3 | 86 (2.0) | 51 (2.3) | 35 (1.7) | |
| T4 | 8 (0.2) | 5 (0.2) | 3 (0.1) | |
| pN stage | 0.592 | |||
| N0 | 3,041 (70.2) | 1,578 (69.9) | 1,463 (70.4) | |
| N1 | 967 (22.3) | 506 (22.4) | 461 (22.2) | |
| N2 | 244 (5.6) | 134 (5.9) | 110 (5.3) | |
| N3 | 81 (1.9) | 38 (1.7) | 43 (2.1) | |
| Chemotherapy | 0.234 | |||
| Yes | 2,606 (60.1) | 1,376 (61.0) | 1,230 (59.2) | |
| No | 1,727 (39.9) | 880 (39.0) | 847 (40.8) | |
| Anthracycline | 0.250 | |||
| Yes | 1,992 (46.0) | 1,056 (46.8) | 936 (45.1) | |
| No | 2,341 (54.0) | 1,200 (53.2) | 1,141 (54.9) | |
| Trastuzumab | 0.593 | |||
| Yes | 206 (4.8) | 111 (4.9) | 95 (4.6) | |
| No | 4,127 (95.2) | 2,145 (95.1) | 1,982 (95.4) |
RT=radiotherapy; BMI=body mass index.