2) the number of lives saved was calculated by applying our mortality reduction estimate to the number of breast cancer deaths expected in the absence of screening.
Therefore we applied the CISNET Stanford model scaled to the observed Norwegian breast cancer mortality reduction to estimate the likely screening effects by age and time since screening.
The absolute mortality reductions are estimated from the NLST results, both directly and extrapolated to long term follow-up as described in the Materials and Methods section.
The estimated mortality reduction in the screening program is similar to the PSE estimates because the long-duration of screening (5 annual or 3 biennial screenings followed by 3 5 years hiatus followed by 5 annual or 3 biennial screenings) in the trial approximated the 21 years of periodic screening.
Take the roughly one-quarter of the estimated mortality reduction was due to "external causes" (injuries, suicide, homicide, complications of medical treatment, and substance abuse).
After correcting for anticonservative and conservative biases, the estimated mortality reduction was 25% (odds ratio = 0.75; 95% confidence interval: 0.49, 1.14; P = 0.09).
Adjusting for self-selection bias using the more conservative intention-to-treat analysis (Duffy et al, 2002) gave a 35% estimated mortality reduction (OR=0.65, 95% CI: 0.48, 0.88; P=0.005).
Use of mammography outside the program, both among nonscreened women and in between 2 screening rounds among screened women, could have reduced the estimated mortality reduction in our study.
They argued that the estimated mortality reduction from screening may be lower than the mortality reduction predicted by MISCAN (van den Akker-van Marle et al, 1999) because of the lower sensitivity of the UK screening programme in the early years of screening.
In addition, we computed the estimated cancer mortality reduction between the two randomized groups (and 95% confidence intervals).
