Breast Magnetic Resonance Imaging Findings in Women Treated with Toremifene for Premenstrual Mastalgia

Background: Toremifene, a selective estrogen receptor modulator, has been shown to be effective in alleviating premenstrual breast pain. However, the exact mechanism by which toremifene and related compounds work in premenstrual mastalgia is poorly understood. Purpose: To find out if the effect of toremifene on breast would be detectable with dynamic magnetic resonance imaging (MRI). Material and Methods: This randomized, double-blind crossover study was performed on women suffering from marked premenstrual mastalgia. Ten women were randomized to receive either toremifene (20 mg) or placebo from cycle day 15 until next menstruation for three menstrual cycles. After a washout period, the treatment was crossed over for three additional cycles. The MRI evaluations were performed premenstrually at the end of each treatment phase. Breast pain and quality-of-life scores were collected from one baseline cycle and from all the treatment cycles. Results: Nine patients were evaluable for this analysis. Both the enhancement ratio and the maximum slope of enhancement tended to be smaller during the toremifene cycles as compared to placebo. On the left side, the difference in the maximum slope of enhancement between toremifene and placebo was statistically significant (median 5.150 [range 3.7-6.7] and 6.500 [range 4.9-9.5], respectively; P = 0.047). T2 relaxation times as well as breast pain and quality-of-life scores were inconsistent. Conclusion: Use of toremifene is associated with measurable changes in dynamic breast MRI findings in women with cyclic breast pain.