Low-dose tamoxifen in the treatment of breast ductal intraepithelial neoplasia: results of a large observational study

Background: Tamoxifen's cost-benefit ratio for breast ductal intraepithelial neoplasia (DIN) is unclear. Since low-dose tamoxifen showed a favorable modulation of breast cancer biomarkers in phase II trials, a monoinstitutional cohort of women with DIN treated with low-dose tamoxifen or no systemic treatment was analyzed. Patients and methods: A total of 309 patients with DIN received low-dose tamoxifen as part of institutional guidelines and were compared with 371 patients with DIN who received no systemic treatment after surgery. Results: Women with estrogen receptor (ER)/progesterone receptor (PgR) >50% DIN who were not treated had a higher incidence of breast events than women on tamoxifen [hazard ratio (HR) 1.76; 95% confidence interval (CI) 1.00-3.12] or women with ER/PgR 50% DIN, recurrence was higher in PgR 6550% DIN than in PgR <50% DIN, whereas it was similar among low PgR (