Table 2.
Relapse and mortality by fractionation schedule: time-to-event analysis (n=4096)
| Cumulative number of events | Estimated cumulative incidence by 5 years (95% CI) | Hazard ratio (95% CI); p value | Estimated absolute difference vs 40 Gy at 5 years (95% CI) | |
|---|---|---|---|---|
| Ipsilateral breast tumour (local) relapse* | ||||
| 40 Gy (n=1361) | 31 (2·3%) | 2·1% (1·4 to 3·1) | 1 (ref) | .. |
| 27 Gy (n=1367) | 27 (2·0%) | 1·7% (1·2 to 2·6) | 0·86 (0·51 to 1·44); 0·56 | −0·3% (−1·0 to 0·9) |
| 26 Gy (n=1368) | 21 (1·5%) | 1·4% (0·9 to 2·2) | 0·67 (0·38 to 1·16); 0·15 | −0·7% (−1·3 to 0·3) |
| Locoregional relapse† | ||||
| 40 Gy (n=1361) | 43 (3·2%) | 2·8% (2·0 to 3·9) | 1 (ref) | .. |
| 27 Gy (n=1367) | 35 (2·6%) | 2·3% (1·6 to 3·3) | 0·80 (0·51 to 1·25); 0·33 | −0·5% (−1·4 to 0·7) |
| 26 Gy (n=1368) | 29 (2·1%) | 1·8% (1·2 to 2·7) | 0·66 (0·41 to 1·06); 0·083 | −0·9% (−1·6 to 0·2) |
| Distant relapse | ||||
| 40 Gy (n=1361) | 59 (4·3%) | 3·8% (2·9 to 5·0) | 1 (ref) | .. |
| 27 Gy (n=1367) | 69 (5·0%) | 4·7% (3·7 to 6·0) | 1·16 (0·82 to 1·64); 0·41 | 0·6% (−0·7 to 2·3) |
| 26 Gy (n=1368) | 76 (5·6%) | 5·1% (4·0 to 6·4) | 1·27 (0·90 to 1·79); 0·17 | 1·0% (−0·4 to 2·9) |
| Any breast cancer-related event‡ | ||||
| 40 Gy (n=1361) | 119 (8·7%) | 7·8% (6·5 to 9·4) | 1 (ref) | .. |
| 27 Gy (n=1367) | 112 (8·2%) | 7·2% (5·9 to 8·7) | 0·93 (0·71 to 1·20); 0·56 | −0·6% (−2·2 to 1·5) |
| 26 Gy (n=1368) | 114 (8·3%) | 7·5% (6·2 to 9·0) | 0·94 (0·73 to 1·22); 0·65 | −0·4% (−2·1 to 1·6) |
| All-cause mortality | ||||
| 40 Gy (n=1361) | 92 (6·8%) | 5·4% (4·3 to 6·8) | 1 (ref) | .. |
| 27 Gy (n=1367) | 105 (7·7%) | 6·9% (5·7 to 8·4) | 1·12 (0·85 to 1·48); 0·42 | 0·6% (−0·8 to 2·5) |
| 26 Gy (n=1368) | 90 (6·6%) | 5·6% (4·5 to 7·0) | 0·96 (0·72 to 1·28); 0·78 | −0·2% (−1·5 to 1·5) |
Hazard ratios less than 1 favour five-fraction schedules. p values were calculated by log-rank test (two-sided).
*
Includes three patients with angiosarcoma in ipsilateral breast (one in the 40 Gy group and two in the 26 Gy group).
†
Defined as ipsilateral breast tumour relapse or regional relapse (axilla, supraclavicular fossa, and internal mammary chain).
‡
Includes local, regional, or distant relapse, breast cancer death, or contralateral breast cancer (disease-free survival).