Table 1.
Characteristics of patients with metastatic breast cancer
| Variable | Training cohort (n=634) | Validation cohort (n=159) | p-value |
|---|---|---|---|
| Age at diagnosis (yr) | |||
| < 35 | 132 (20.8) | 25 (15.7) | 0.127 |
| 35-50 | 300 (47.3) | 71 (44.7) | |
| > 50 | 202 (31.9) | 63 (39.6) | |
| Menopause status | |||
| Premenopausal | 434 (68.5) | 99 (62.7) | 0.185 |
| Menopausal | 200 (31.5) | 60 (37.3) | |
| Tumour size (cm) | |||
| ≤ 2 | 128 (20.2) | 27 (17.0) | 0.373 |
| > 2 and ≤ 5 | 261 (41.2) | 78 (49.1) | |
| > 5 | 147 (23.2) | 41 (25.8) | |
| Unknown | 98 (15.5) | 13 (8.2) | |
| Axillary lymph node involvement | |||
| Yes | 483 (76.2) | 123 (77.4) | 0.242 |
| No | 139 (21.9) | 36 (22.6) | |
| Unknown | 12 (1.9) | 0 | |
| MFI | |||
| Primary stage IV | 194 (30.6) | 64 (40.3) | < 0.001 |
| < 6 mo | 57 (9.0) | 17 (10.7) | |
| 6 mo-2 yr | 203 (32.0) | 23 (14.5) | |
| 2-5 yr | 146 (23.0) | 50 (31.4) | |
| > 5 yr | 34 (5.4) | 5 (3.1) | |
| No. of metastases | |||
| 1 | 382 (60.3) | 84 (52.8) | 0.105 |
| > 1 | 252 (39.7) | 75 (47.2) | |
| Metastasis sites | |||
| Visceral or CNS | 191 (30.1) | 38 (23.9) | 0.243 |
| Bone or soft tissue | 234 (36.9) | 60 (37.7) | |
| Multiple | 209 (33.0) | 61 (38.4) | |
| Hormone receptor status | |||
| HR+ | 432 (68.1) | 107 (67.3) | 0.850 |
| HR- | 202 (31.9) | 52 (32.7) | |
| HER2 receptor status | |||
| Amplified | 213 (33.6) | 57 (35.8) | 0.261 |
| Non-amplified | 369 (58.2) | 95 (59.7) | |
| Equivocal (2+) | 52 (8.2) | 7 (4.5) | |
| Type of surgery | |||
| MRM | 525 (82.8) | 120 (75.5) | 0.103 |
| BCT | 23 (3.6) | 4 (2.5) | |
| Tumour resection | 5 (0.8) | 2 (1.2) | |
| No | 81 (12.8) | 33 (20.8) | |
| Endocrine therapy | |||
| Yes | 381 (60.1) | 76 (47.8) | 0.002 |
| No | 194 (30.6) | 54 (34.0) | |
| Unknown | 59 (9.3) | 29 (18.2) | |
| Anti-HER2 therapy | |||
| Yes | 117 (18.5) | 31 (19.5) | 0.978 |
| No | 509 (80.3) | 125 (78.6) | |
| Unknown | 8 (1.3) | 3 (1.9) | |
| Chemotherapy (first-line regimen) | |||
| Yes | 616 (97.2) | 151 (95.0) | 0.082 |
| No | 16 (2.5) | 5 (3.1) | |
| Unknown | 2 (0.3) | 3 (1.9) | |
| Radiotherapy | |||
| Yes | 328 (51.7) | 63 (60.4) | 0.008 |
| No | 305 (48.1) | 96 (39.6) | |
| Unknown | 1 (0.2) | 0 | |
| Vital status | |||
| Alive | 286 (45.1) | 104 (65.4) | < 0.001 |
| Death | 348 (54.9) | 55 (34.6) |
Values are presented as number (%). MFI, metastasis-free interval; CNS, central nervous system; HR, hormone receptor; HER2, human epidermal growth factor receptor 2; MRM, modified radical mastectomy; BCT, breast conserving therapy.