Intrauterine Levonorgestrel Protects Against Uterine Effects of Tamoxifen

NEW YORK DEC 21, 2007 (Reuters Health) - Prophylactic use of a levonorgestrel intrauterine system (LNG-IUS) reduces the occurrence of de novo endometrial polyps in women treated with tamoxifen for breast cancer, according to first-year interim results of a randomized controlled trial.

Tamoxifen exerts weak estrogenic effects on the endometrium, Dr. S. S. C. Chan from The Chinese University of Hong Kong and colleagues note in the December issue of BJOG: An International Journal of Obstetrics and Gynecology.

The authors note that progestogen therapy is well established for treating endometrial hyperplasia, and the LNG-IUS delivers a high concentration of progestogen to endometrial tissues without adverse systemic effects.

In a recent study, LNG-IUS, introduced more than 12 months after initiation of tamoxifen, had a protective effect on the endometrium of postmenopausal women. In nearly 30% of these women, endometrial polyps and hyperplasia had already occurred.

Dr. Chan and colleagues are in the midst of a 5-year study investigating the endometrial effects of LNG-IUS inserted prior to tamoxifen treatment. They randomized 66 premenopausal and 47 postmenopausal women who required tamoxifen after breast cancer treatment to prophylactic LNG-IUS or a control group.

The team performed outpatient hysteroscopy and endometrial biopsy before and at 12 months after commencement of tamoxifen.

At one year, women in the LNG-IUS group had a significantly lower incidence of endometrial polyp (1.8% vs 15.5%, p = 0.017). The relative risk of endometrial polyp with LNG-IUS was 0.12.

There was no significant between-group difference LNG in the incidence of submucosal fibroid (1.8% vs 3.4%, p = 1.0).

These early data suggest that LNG-IUS insertion prior to tamoxifen treatment "effectively reduces the estrogenic effect of tamoxifen on the endometrium," Dr. Chan and colleagues note.

They also note that while vaginal spotting was common in the first 6 months among both premenopausal and postmenopausal women, "most found it acceptable and have agreed to continue with the study beyond 1 year."

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