Demographics of included patients
| Variables | Low-risk group | High-risk group | ||||
| No RT | RT | Total | No RT | RT | Total | |
| TILs | ||||||
| Low | 240 (81.4%) | 225 (80.9%) | 465 (81.2%) | 63 (44.4%) | 49 (45.0%) | 112 (44.6%) |
| High | 55 (18.6%) | 53 (19.1%) | 108 (18.8%) | 79 (55.6%) | 60 (55.0%) | 139 (55.4%) |
| PD-1 | ||||||
| Low | 267 (90.5%) | 258 (92.8%) | 525 (91.6%) | 109 (76.8%) | 80 (73.4%) | 189 (75.3%) |
| High | 28 (9.5%) | 20 (7.2%) | 48 (8.4%) | 33 (23.2%) | 29 (26.6%) | 62 (24.7%) |
| PD-L1 | ||||||
| Low | 255 (86.4%) | 256 (92.1%) | 511 (89.2%) | 89 (62.7%) | 61 (56.0%) | 150 (59.8%) |
| High | 40 (13.6%) | 22 (7.9%) | 62 (10.8%) | 53 (37.3%) | 48 (44.0%) | 101 (40.2%) |
| Immune activation | ||||||
| Active* | 20 (6.8%) | 9 (3.2%) | 29 (5.1%) | 50 (35.2%) | 46 (42.2%) | 96 (38.2%) |
| Inactive/absent† | 275 (93.2%) | 269 (96.8%) | 544 (94.9%) | 92 (64.8%) | 63 (57.8%) | 155 (61.8%) |
| Subtype | ||||||
| HER2-positive‡ | 6 (2.2%) | 9 (3.5%) | 15 (2.8%) | 19 (16.2%) | 19 (21.6%) | 38 (18.5%) |
| Luminal A | 193 (71%) | 175 (67.8%) | 368 (69.4%) | 26 (22.2%) | 18 (20.5%) | 44 (21.5%) |
| Luminal B | 70 (25.7%) | 72 (27.9%) | 142 (26.8%) | 37 (31.6%) | 27 (30.7%) | 64 (31.2%) |
| Triple-negative | 3 (1.1%) | 2 (0.8%) | 5 (0.9%) | 35 (29.9%) | 24 (27.3%) | 59 (28.8%) |
| ER status | ||||||
| Negative | 7 (2.6%) | 5 (1.9%) | 12 (2.3%) | 42 (35.3%) | 33 (37.1%) | 75 (36.1%) |
| Positive | 266 (97.4%) | 254 (98.1%) | 520 (97.7%) | 77 (64.7%) | 56 (62.9%) | 133 (63.9%) |
| PgR status | ||||||
| Negative | 41 (15.0%) | 48 (18.5%) | 89 (16.7%) | 59 (49.6%) | 48 (53.9%) | 107 (51.4%) |
| Positive | 232 (85.0%) | 211 (81.5%) | 443 (83.3%) | 60 (50.4%) | 41 (46.1%) | 101 (48.6%) |
| Histological grade | ||||||
| Grade I | 68 (23.1%) | 73 (26.3%) | 141 (24.6%) | 0 (0%) | 0 (0%) | 0 (0%) |
| Grade II | 227 (76.9%) | 205 (73.7%) | 432 (75.4%) | 10 (7.0%) | 9 (8.3%) | 19 (7.6%) |
| Grade III | 0 (0%) | 0 (0%) | 0 (0%) | 132 (93.0%) | 100 (91.7%) | 232 (92.4%) |
| Endocrine therapy | ||||||
| No hormone therapy | 254 (92.7%) | 249 (95.8%) | 503 (94.2%) | 105 (88.2%) | 80 (88.9%) | 185 (88.5%) |
| Hormone therapy | 20 (7.3%) | 11 (4.2%) | 31 (5.8%) | 14 (11.8%) | 10 (11.1%) | 24 (11.5%) |
| Chemotherapy | ||||||
| No chemotherapy | 274 (100%) | 259 (99.6%) | 533 (99.8%) | 113 (95.0%) | 87 (96.7%) | 200 (95.7%) |
| Chemotherapy | 0 (0%) | 1 (0.4%) | 1 (0.2%) | 6 (5.0%) | 3 (3.3%) | 9 (4.3%) |
| IBTR within 5 years§ | ||||||
| No IBTR | 240 (81.4%) | 255 (91.7%) | 495 (86.4%) | 96 (67.6%) | 86 (78.9%) | 182 (72.5%) |
| IBTR | 37 (12.5%) | 7 (2.5%) | 44 (7.7%) | 27 (19.0%) | 8 (7.3%) | 35 (13.9%) |
| Censored | 18 (6.1%) | 16 (5.8%) | 34 (5.9%) | 19 (13.4%) | 15 (13.8%) | 34 (13.5%) |
| IBTR within 10 years§ | ||||||
| No IBTR | 206 (69.8%) | 221 (79.5%) | 427 (74.5%) | 80 (56.3%) | 69 (63.3%) | 149 (59.4%) |
| IBTR | 54 (18.3%) | 23 (8.3%) | 77 (13.4%) | 33 (23.2%) | 10 (9.2%) | 43 (17.1%) |
| Censored | 35 (11.9%) | 34 (12.2%) | 69 (12.0%) | 29 (20.4%) | 30 (27.5%) | 59 (23.5%) |
*Defined as TILs ≥10% and PD-L1 and/or PD-1 ≥1%.
†Defined as TILs <10% or TILs ≥10% but PD-L1 and PD-1 <1%.
‡Includes both ER-positive and ER-negative tumors.
§Reported as absolute frequencies rather than cumulative incidences.
ER, estrogen receptor; HER2, human epidermal growth factor receptor 2; IBTR, ipsilateral breast tumor recurrence; PD-1, programmed cell death protein-1 ; PD-L1, programmed death ligand-1 ; PgR, progesterone receptor; RT, radiotherapy; TILs, tumor-infiltrating lymphocytes.