False-positives and unnecessary biopsies from an estimated cohort of women in a breast screening program for 7 years of screening*47
| Age range, yr | ||||
|---|---|---|---|---|
| Outcome | 40–49 | 50–59 | 60–69 | 70–74 |
| Per 1000 women screened† | ||||
| FP mammography | 294 | 294 | 256 | 219 |
| Biopsies on FP | 43 | 37 | 35 | 30 |
| Per 1 breast cancer death prevented | ||||
| FP mammography (based on 3 cycles of screening)† | 508 | 392 (M) | 278 | 141 |
| Biopsies on FP (based on 3 cycles of screening)† | 74 | 50 (M) | 38 | 19 |
Note: FP = false-positive, M = calculated using the moderate baseline risk for this age group.15
↵* As the median duration of screening trials was 7 years (range 3–12 yr), the impact of this duration of screening on benefits and harms was used. The data are used to approximate a cohort of women entering the screening program.47 Although assumed, but not confirmed, the “initial screen” in the Canadian Partnership Against Cancer report is the first screen documented in the database and may not necessarily be the first “true” screen of a woman. This is especially true for data originating from Alberta.
↵† Three cycles of screening for which women are screened every 2–3 years, for a total of 6–9 years of a screening period. Calculation: Initial screening cycle + 2 (subsequent screening cycle) to estimate harms occurring with 7 years of screening.