Breast cancer risk assessment in women aged 70 and older

Abstract

Although the benefit of screening mammography for women over 69 has not been established, it is generally agreed that screening recommendations for older women should be individualized based on health status and breast cancer risk. However, statistical models to assess breast cancer risk have not been previously evaluated in this age group. In this study, the original Gail model and three more recent models that include mammographic breast density as a risk factor were applied to a cohort of 19,779 Vermont women aged 70 and older. Women were followed for an average of 7.1 years and 821 developed breast cancer. The predictive accuracy of each risk model was measured by its c-statistic and associations between individual risk factors and breast cancer risk were assessed by Cox regression. C-statistics were 0.54 (95% CI = 0.52–0.56) for the Gail model, 0.54 (95% CI = 0.51–0.56) for the Tice modification of the Gail model, 0.55 (95% CI = 0.53–0.58) for a model developed by Barlow and 0.55 (95% CI = 0.53–0.58) for a Vermont model. These results indicate that the models are not useful for assessing risk in women aged 70 and older. Several risk factors in the models were not significantly associated with outcome in the cohort, while others were significantly related to outcome but had smaller relative risks than estimated by the models. Age-related attenuation of the effects of some risk factors makes the prediction of breast cancer in older women particularly difficult.