Adjuvant Tamoxifen ( Nolvadex ) reduces the risk of breast cancer recurrence in women with estrogen receptor-positive breast carcinoma. Tamoxifen also increases the risk of postmenopausal bleeding, endometrial hyperplasia, polyps, and endometrial cancer.
The Levonorgestrel-releasing intrauterine system ( LNG-IUS; Mirena ) causes profound endometrial suppression.

A systematic review has determined the effectiveness of the Levonorgestrel intrauterine system in preventing the development of endometrial hyperplasia, polyps, and adenocarcinoma in pre and postmenopausal women taking adjuvant Tamoxifen following breast cancer.

Only two randomised controlled trials were identified and are included in the review.

The outcome measures were endometrial pathology ( including polyps, endometrial hyperplasia, or adenocarcinoma ) diagnosed at hysteroscopy or endometrial biopsy; any reported side effects of treatment; and abnormal vaginal bleeding.

In both included studies, the active treatment arm was the Mirena 20 mug/day Levonorgestrel-releasing intrauterine device. The LNG-IUS in Tamoxifen users led to a significant reduction in the incidence of endometrial polyps ( Peto odds ratio 0.14 ).
Neither trial was sufficiently powered to detect whether LNG-IUS leads to significant changes in the incidence of endometrial hyperplasia or adenocarcinoma in Tamoxifen users, nor whether Levonorgestrel-releasing intrauterine system leads to any increased risk of breast cancer recurrence. There appeared to be more vaginal bleeding in the Mirena treatment group, in the first six months only. However, the bleeding patterns at 12 months were fairly similar for both groups.

In conclusion, the Mirena LNG-IUS appears to prevent the development of benign endometrial polyps in breast carcinoma patients taking Tamoxifen, over a one-year period. There is no clear evidence from the available randomised controlled trials that LNG-IUS prevents endometrial hyperplasia or adenocarcinoma in these patients. Larger studies are necessary to assess the effects of Levonorgestrel-releasing intrauterine system in preventing endometrial hyperplasia and endometrial cancer, and to determine whether LNG-IUS might have an impact on the risk of breast cancer recurrence.

Chin J et al, Cochrane Database Syst Rev 2009;(4):CD007245

XagenaMedicine2009


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