In many highly developed countries, improving chances of survival are the main driver of population aging (Preston and Stokes 2012); the increase in life expectancy at birth is due to mortality reductions at all ages, though the highest gains in mortality reductions advance to successively older ages (Christensen et al. 2009).
Harm reduction gained prominence with the AIDS epidemic.
While the predicted mortality reduction and life years gained attributed to screening did not vary much across risk factor assumptions, there were small differences in the predicted increase in life years gained resulting from a shift to screening initiation at age 45 rather than a later initiation at age 50 years.
Breast cancer mortality reduction and life-years gained were considered as screening benefits, whereas, overdiagnosis and false positive results were assessed as harms.
In a previous work we analyzed the benefit, in terms of mortality reduction and years of life gained, of different screening strategies in Catalonia [ 10] using the Lee and Zelen stochastic models [ 11, 12].
Limitations of this study include the lack of identification of optimal risk thresholds, as this requires additional information on the long-term benefits (e.g., life-years gained and mortality reduction) and harms (e.g., overdiagnosis) of risk-based screening strategies using these models.
In all cases, earlier initiation of screening resulted in both a greater mortality reduction and more life years gained per 1000 individuals screened (LYG).
For each risk factor cohort, we calculated the mortality reduction (MR) and life years gained (LYG) per 1000 individuals attributable to screening by comparing screened to unscreened cohorts up the each individual's 80th birthday.
Using the calibrated model, predictions of the number of screens, number of screen detected and interval cancers, the stage distribution, the mortality reduction and the life years gained will be made for the different screening arms in the study.
For a decade of annual mammographic screening starting at age 40 years, net gains in years of life were estimated for both a 10 and 20% mortality reduction, although the net gain was small for all women (7 20 years per 1000 women screened) compared with the estimated net gain for a decade of screening starting at age 50 years (42 years per 1000 women screened).
