Prophylactic use of levonorgestrel-releasing intrauterine system in women with breast cancer treated with tamoxifen: a randomized controlled trial.

To estimate the rate of endometrial pathology with the prophylactic use of levonorgestrel-releasing intrauterine system in women with breast cancer treated with tamoxifen. This was a randomized contro-lled trial of 129 Chinese women who attended a university hospital in Hong Kong and required adjuvant tamoxifen for breast cancer after the completion of postoperative radiotherapy and chemotherapy. Women were randomized to treatment (prophylactic levonorgestrel-releasing intrauterine system insertion before the commencement of tamoxifen) or control group. The uterine cavity was examined by hysteroscopy and endometrial sampling before the commencement of tamoxifen and at 12, 24, 45, and 60 months afterward. Any endometrial polyps or submucosal fibroids were resected through hysteroscopy at each assessment and specimens were sent for histologic confirmation. A total of 94 women completed 5-year follow-up. There was no significant difference in the occurrence of submucosal fibroids (1 [1.8%] compared with 2 [3.4%]) and endometrial hyperplasia (both 0) in the treatment and control groups, respectively. Levonorgestrel-releasing intrauterine system significantly reduced de novo endometrial polyps (hazard ratio 0.19, 95% confidence interval 0.07-0.48) over the course of 5 years on an intention-to-treat basis. There was no statistically significant increase in breast cancer recurrence rate (10 [17.2%] compared with 6 [10.0%]) or cancer-related deaths (6 [10.3%] compared with 5 [8.3%]) in the treatment group, but the study was underpowered in this regard. Prophylactic levonorgestrel-releasing intrauterine system prevents de novo endometrial polyps in women using tamoxifen. However, its role in the prevention of endometrial hyperplasia and adenocarcinoma as well as its effect on risk of breast cancer recurrence remain uncertain. Chinese Clinical Trial Registry, http://www.chictr.org/en/, ChiCTR-TRC-09000625. I.