Abstract P4-11-03: Effect of tamoxifen and raloxifene on proliferative activity of breast epithelium in premenopausal women

Abstract

Abstract Background: Both Tamoxifen and raloxifene have been demonstrated to be effective to reduce the incidence of breast cancer among women. Objective: To compare the effects of raloxifene (60 mg/day) and tamoxifen (20 mg/day) on the proliferative activity of normal human breast epithelium, during the luteal phase of the menstrual cycle, by means of the immunoexpression of Ki-67/MIB-1. Patients and Methods: Forty-eight women presenting benign breast nodules with an indication for lesion excision took part in this study. These women were randomized to use tamoxifen or raloxifene for 22 days. They underwent surgery after using the medication, and a one-centimeter fragment of normal breast tissue was removed to study the immunoexpression of Ki-67. For this, the frequency of cells immunolabeled for Ki-67/MIB-1 per thousand epithelial cells was quantified. Results: The mean percentage ratios between immunolabeled and non-labeled cells were 2.02 (±1.09) and 3.13 (±3.23) for the tamoxifen and raloxifene groups, respectively. There was no statistically significant difference between the two groups, tamoxifen (n = 16) and raloxifene (n = 14), in relation to the immunoexpression of Ki-67 (p = 0.205). The mean of progesterone level was 19.62 (±17.67) for the tamoxifen group and 14.59 (±8.98) for the raloxefene group (p = 0.32). The plasma levels of estradiol, the values found were: 355.72 (± 337.98) and 171.02 (± 119.83) for groups of tamoxifen e raloxifene groups, respectively (p = 0.055). Conclusion: In this study, we observed that there was no difference in the potential for reducing the proliferative activity of normal breast epithelium between tamoxifen and raloxifene in premenopausal women. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-11-03.