doi: 10.1093/aje/kwx178. 

Abstract

Previous studies have linked reductions in mammographic density after a breast cancer diagnosis to an improved prognosis. These studies focused on short-term change, using a two-stage process, treating estimated change as a fixed covariate in a survival model. We propose the use of a joint longitudinal-survival model. This enables us to model long-term trends in density while accounting for drop-out as well as for measurement error. We study the change in mammographic density after a breastcancer diagnosis and its association with prognosis (measured by cause-specific mortality), overall and with respect to hormone replacement therapy and tamoxifen treatment. We included 1740 women diagnosed with breast cancer in Sweden in 1993-1995, aged 50-74, with follow-up until 2008. They had in total 6317 mammographicdensity measures available from the first 5 years of follow-up, including baseline measures. We found that the impact of hormone replacement therapy withdrawal was larger than that of tamoxifen treatment on densityreduction. Unlike previous studies, we found that there was an association between density reduction and survival, both for tamoxifen treated and non-treated women.