Changes in the sonographic appearance of the uterus after discontinuation of tamoxifen therapy

Objective. The purpose of this study was to assess the duration of sonographically detected changes in the endometrium of women with a history of tamoxifen use. Methods. Patients with breast cancer who had a history of tamoxifen use and documented pelvic sonographic studies were identified by means of clinic databases in both the Section of Gynecological Oncology and the Section of Obstetrical and Gynecological Ultrasound, University of Chicago, between January 1, 1996, and March 30, 2004. Of the 99 patients who met study criteria, 34 had discontinued tamoxifen use before the sonographic evaluation. Each patient's age, gravity and parity, weight, ethnicity, duration and dose of drug use, interval from drug discontinuation until sonographic evaluation, and uterine pathologic findings were reviewed. Endometrial thickness as assessed by pelvic sonography was examined in relation to duration of tamoxifen use and time from discontinuation of the drug. Statistical analysis was performed with linear regression and mixed effect linear regression models. Results. Endometrial thickness increased with increasing duration of tamoxifen use at a rate of 0.75 mm/y. The mean endometrial thickness after approximately 5 years of tamoxifen use was 12 mm (range, 6-21 mm). After discontinuation of tamoxifen, endometrial thickness decreased by 1.27 mm/y. Conclusions. Endometrial thickness as measured by pelvic ultrasound examination increases with the duration of tamoxifen use. After discontinuation of the drug, the measured thickness decreases but at a very slow rate.