Trial of Low Dose Tamoxifen in Women With Breast Intraepithelial Neoplasia - Long Term Follow-up

The aim of the study is to evaluate whether tamoxifen at a low dose of 5mg/d reduces in the long term the incidence of invasive breast cancer and ductal carcinoma in situ, DCIS (DIN 1c, 2, 3) of the breast, in woman operated for lobular intraepithelial neoplasia (LIN1, 2 and 3) or ER-positive ductal intraepithelial neoplasia (DIN 1b, DIN2, DIN3, 1a excluded) of the breast. To improve the risk-benefit ratio, the use of lower doses of the drug has been proposed. Biomarker trials revealed that 5 mg/d was noninferior to 20 mg/d in inhibiting proliferation of breast cancer and normal endometrial tissue. By contrast, the risk of endometrial cancer si dose-dependent, and the dose reduction can lead a substantial decrease. Morover a dose of 5 mg/day is associated with an overall decrease of the estrogenic activity of tamoxifen on insulin like growth factor (IGF-I), sex hormone-binding globulin (SHBG) and antithrombin-III, with a decrease of venous thromboembolic events. Moreover, tamoxifen exhibits a high tissue distribution, so that a dose of 5 mg/day attains at the breast tissue level a concentration 10 times higher than that needed to inhibit cell growth in vitro. A prospective cohort study also showed that 10 mg on alternate days halves recurrence of DCIS in postmenopausal women. It has been shown that the treatment of dysplasia or pre-cancer drives the reduction of the invasive neoplasms onset. This is a chemoprevention trial designed to validatate the low-dose Tamoxifen in women with diseases at high evolutionary risk. The demonstration of efficacy and safety of such a treatment for the prevention of the invasive breast cancer would lead improvements in term of survival and quality of life for the patients at increased risk.