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Wolfson Institute of Preventive Medicine - Barts and The London

Decrease in breast density continues for up to five years from start of Tamoxifen breast cancer prevention therapy

A study of women at increased risk of breast cancer who take the preventive drug Tamoxifen has found a consistent and large average reduction in breast density over the first year of treatment, and a continued reduction for up to four years thereafter. Tamoxifen is known to reduce mammographic density, and there is some evidence that women with the largest reductions benefit most from this preventive therapy. This study showed similar average declines in mammographic density across four different fully-automated methods, but also found that breast density change on an individual basis was not stable enough to be used as a basis for personalised clinical decisions to be made at one year.

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Wolfson authors led the statistical analysis of the study, which was carried out at the University of Manchester and Manchester NHS Foundation Trust. Breast density was measured annually in two groups of premenopausal women at increased breast cancer risk, one group receiving Tamoxifen and the other not. Four automated methods were used to measure density on mammograms from the 298 women over an average of three years.

Author Dr Adam Brentnall said: “These findings will be important to clinicians and patients considering endocrine therapy, and to regulators and ethics boards considering trials of products that require information on the reliability and stability of breast density reductions as an endpoint.” 

Mammographic density change in a cohort of premenopausal women receiving tamoxifen for breast cancer prevention over five years. AR Brentnall, R Warren, EF Harkness, SM Astley, J Wiseman, J Fox, L Fox, M Eriksson, P Hall, J Cuzick, DG Evans, A Howell. Breast Cancer Res 2020;22:101.  

This work was supported by funding from the NIHR, Genesis Breast Cancer Prevention, and Cancer Research UK.