Table 2.

Number of mammogram examinations needed to prevent one death.*

Age	10% RRR†	15% RRR	20% RRR	Range 20%‡	25% RRR	30% RRR
40	11050	7370	5530	2820–11630	4420	3680
45	7700	5130	3850	1980–8070	3080	2570
50	5950	3970	2970	1540–6160	2380	1980
55	5000	3330	2500	1320–5100	2000	1670
60	4460	2970	2230	1200–4450	1780	1490
65	4120	2750	2060	1130–4020	1650	1370

* Number of examinations is 5.25 times the number need to screen repeatedly (NNSR), which is the reciprocal of the reduction in absolute death risk (RADR) in Figure 1. The number needed to screen once (NNSO) is equivalent to the number of examinations if the benefit is the same for all mammograms. The average benefit of a subsequent screen is the inverse of the NNSO.

^† The 5.25 median screens from the trials are responsible for the relative risk reduction (RRR) for repeated screening. We assumed the baseline exam has twice the benefit of a subsequent exam [11,29,33].

^‡ The range is calculated by using interval analysis.