Table 2.
Cumulative incidence of breast cancer by trial group, cancer type, and follow-up period
|
Intervention group |
Control group |
Intervention group vs control group, RR (95% CI) | |||
|---|---|---|---|---|---|
| Breast cancers, n | Follow-up, person-years | Breast cancers, n | Follow-up, person-years | ||
| Invasive cancers only | |||||
| Intervention period | 835 | 569 632 | 1628 | 1 129 985 | 1·02 (0·94–1·11) |
| Up to and including first NHSBSP screen | 970 | 569 632 | 2021 | 1 129 985 | 0·95 (0·88–1·04) |
| By the end of follow-up | 2288 | 1 177 990 | 4640 | 2 339 852 | 0·98 (0·93–1·03) |
| In-situ cancers only | |||||
| Intervention period | 118 | 573 221 | 103 | 1 137 432 | 2·27 (1·75–2·95) |
| Up to and including first NHSBSP screen | 155 | 573 221 | 226 | 1 137 432 | 1·36 (1·11–1·67) |
| By the end of follow-up | 329 | 1 195 224 | 620 | 2 375 349 | 1·05 (0·92–1·20) |
| All cancers | |||||
| Intervention period | 953 | 569 016 | 1731 | 1 129 491 | 1·09 (1·00–1·19) |
| Up to and including first NHSBSP screen | 1125 | 569 016 | 2247 | 1 129 491 | 0·99 (0·93–1·07) |
| By the end of follow-up | 2617 | 1 174 649 | 5260 | 2 334 516 | 0·99 (0·94–1·04) |
Intervention period was defined as the period from randomisation up to immediately before first NHSBSP screen. RRs and 95% CIs are for incidence of breast cancer in intervention group compared with control group. RR=relative rate. NHSBSP=National Health Service Breast Screening Programme.