Effects of tamoxifen and aromatase inhibitors on breast tissue enhancement in dynamic contrast-enhanced breast MR imaging: a longitudinal intraindividual cohort study

Abstract

Purpose: To prospectively investigate the effects of two antihormonal medications, tamoxifen and aromatase inhibitor (AI), on the degree of background enhancement in breast magnetic resonance (MR) imaging.

Materials and methods: This institutional review board-approved study was performed in 40 postmenopausal women (mean age, 63 years; range, 49-78 years) with unilateral breast cancer between January 2005 and December 2010. Informed consent was obtained from all participants. All patients underwent breast MR imaging before starting any medication, under tamoxifen, and after switching to an AI. Qualitative and quantitative degrees of benign parenchymal enhancement were investigated before treatment, under tamoxifen, and under AI. Data were analyzed by using the Wilcoxon singed-rank test and Student t test for matched pairs.

Results: Before treatment, the distribution of background enhancement MR-American College of Radiology (ACR) categories 1, 2, 3, and 4 was 20%, 35%, 33%, and 13%, respectively. With tamoxifen, background enhancement was suppressed, with a distribution of 80%, 15%, 5%, and 0% for MR-ACR categories 1, 2, 3, and 4, respectively. With AI, background enhancement recovered in part, with a distribution of 25%, 53%, 23%, and 0% for categories 1, 2, 3, and 4, respectively. In all 40 women, background enhancement rates were highest before treatment (mean, 51.3% ± 33.3 [standard deviation]). By using tamoxifen, background enhancement rates were significantly reduced (mean, 8.4% ± 9.2), and rose again after the switch to an AI (mean, 22.9% ± 19.1 [P < .001]). Prevalence of benign enhancing foci was 65% (26 of 40) at baseline, 12.5% (five of 40) with tamoxifen, and 40% (16 of 40) with AI.

Conclusion: The effects of tamoxifen and AI on benign parenchymal enhancement differ. Whereas tamoxifen leads to a virtually complete suppression of enhancement, the effects of AI are less pronounced. Accordingly, whereas enhancement is unusual and deserves a more careful work-up in a patient in whom tamoxifen is used, this is not necessarily true for women in whom AIs are used. Online supplemental material is available for this article.