Chapter 14: Impact of Mammography on U.S. Breast Cancer Mortality, 1975-2000: Are Intermediate Outcome Measures Informative?

Seven models have estimated the contribution of screening to the decrease in U.S. breast cancer mortality between 1975 and 2000. We will investigate whether the model estimates of the mortality reduction due to screening are associated with intermediate outcome measures (IOMs). Detection rates at screening, 1- and 2-year sensitivity, program sensitivity, and incidence of advanced tumors are used as IOMs. Moreover, the model parameters preclinical duration and sensitivity are analyzed. The correlation of IOMs with mortality is assessed for actual U.S. screening and for an intensive screening scenario, with annual screening at ages 40-79 years with 100% participation. Also, 12 alternative screening scenarios are run for one of the models, and within-model correlation between IOMs and mortality reduction is described. Resulting correlations between IOMs and mortality reduction are mostly weak. For 2-year sensitivity and the incidence of advanced tumors, correlations are high in the intensive screening scenario. Within-model correlations are strong for incidence of advanced tumors and program sensitivity. Intermediate outcome measures have limited potential in predicting the impact of mammographic screening on mortality. Incidence of advanced tumors and program sensitivity are measures that merit further consideration as surrogates for mortality reduction.