Table 2.
Year-to-Year Breast-Cancer Incidence and Means of Detection before and after Intervention Ended, According to Study Group.*
| Variable | Interval before Intervention Ended | Interval after Intervention Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2 to <3 yr | 1 to <2 yr | <1 yr | <1 yr | 1 to <2 yr | 2 yr to End of Trial | |||||||
|
Hormone Therapy |
Placebo |
Hormone Therapy |
Placebo |
Hormone Therapy |
Placebo |
Hormone Therapy |
Placebo |
Hormone Therapy |
Placebo |
Hormone Therapy |
Placebo | |
| Breast cancer | ||||||||||||
| No. at risk | 8245 | 7846 | 8113 | 7752 | 7990 | 7643 | 7854 | 7533 | 7647 | 7369 | 7466 | 7190 |
| Mean follow-up (mo) | 11.9 | 12.0 | 11.9 | 11.9 | 11.9 | 11.9 | 11.8 | 11.8 | 11.9 | 11.9 | 5.6 | 5.6 |
| No. of cases | 38 | 23 | 45 | 23 | 48 | 31 | 34 | 27 | 28 | 19 | 17 | 14 |
| Annualized incidence (%)† | 0.46 | 0.29 | 0.56 | 0.30 | 0.61 | 0.41 | 0.44 | 0.36 | 0.37 | 0.26 | 0.49 | 0.42 |
| Hazard ratio (95% CI)‡ | 1.59 (0.95–2.67) | 1.88 (1.14–3.11) | 1.48 (0.94–2.33) | 1.20 (0.72–1.99) | 1.43 (0.80–2.57) | 1.19 (0.59–2.42) | ||||||
| Means of detection — % | ||||||||||||
| Mammogram§ | 84 | 84 | 83 | 82 | 83 | 83 | 80 | 80 | 78 | 78 | 71 | 70 |
| Breast biopsy¶ | 2.7 | 1.5 | 2.8 | 1.5 | 3.0 | 1.6 | 3.3 | 1.8 | 2.2 | 1.4 | 1.5 | 1.1 |
Summary statistics for the intervention phase are based on all 16,608 participants in the trial, and those for the postintervention phase are based on the 15,387 participants for whom postintervention follow-up data were available.
Annualized incidence was computed according to time period, where the total number of events for patients at risk for invasive breast cancer during a particular time period was divided by the total follow-up time. Follow-up time is defined as the time elapsed between the start of each period and the first occurrence of invasive breast cancer or censoring (death, loss to follow-up, or the end of each time period).
Hazard ratios were calculated with the use of a Cox proportional-hazards model for the effect on the risk of breast cancer in the hormone-therapy group as compared with the placebo group, stratified according to age and randomized assignment in the diet-modification trial.
The data on mammograms are based on the trial protocol for scheduled annual mammograms.
The data on breast biopsies were self-reported.