Usefulness of SERMs for Uterine Fibroids Still Unestablished

The available evidence that selective estrogen receptor modulators (SERMs) can reduce the size of fibroids or improve clinical symptoms is inconsistent, according to the results of an updated intervention review conducted by the Cochrane Menstrual Disorders and Subfertility Group.¹

Fibroid growth has been observed to be largely hormone dependent, and current medical treatments, therefore, generally involve manipulations of various hormones to reduce the size of fibroids. Of the hormone-based therapies, the most commonly used is gonadotropin-releasing hormones, which effectively reduce tumor size but can only be used for short periods. GnRH also is associated with significant adverse effects, and tumors regrow once treatment is discontinued.

The clinical expectation of SERMs in the management of symptomatic uterine fibroids is that these hormone-like medications would shrink the fibroid without provoking a menopausal state or triggering additional growth of the fibroid. Unlike with GnRH, regrowth of the fibroid is unlikely after SERM treatment ends. However, the studies that have evaluated SERMs versus other forms of medical therapy, placebo, or no treatment in premenopausal women of reproductive age who have uterine fibroids are limited.

In this updated review, 3 studies involving 215 women were included. All of these studies had relatively small sample sizes, ranging from 25 to 100 women, and raloxifene was the SERM being evaluated in all included studies. In one trial, one study arm received raloxifene and a GnRH analog and the other study arm received a GnRH analog alone.

The review authors found that raloxifene was associated with a significant decrease in fibroid size in 2 of the studies, but raloxifene was associated with no benefit in the third study at the 3-month and 6-month follow-ups. All 3 studies cited adverse effects related to raloxifene use, but specific details about their type and prevalence were not reported. The overall evidence quality was low at best, reported the review authors. In addition, the dissimilar methodology of the 3 included studies made performing a meta-analysis impossible.

In theory, SERMs, which are an estrogen receptor ligand that offer selective antagonistic or agonistic effects, seem perfectly suited for the management of uterine fibroids.² However, there effectiveness is controversial, and data for their effectiveness and safety in women of reproductive age are lacking.

Pertinent Point:
- Selective estrogen receptor modulators (SERMs) may have some usefulness in the management of symptomatic fibroids in women who want to retain their fertility, but additional studies are needed to establish evidence of their benefit.

References:

1. Deng L, Wu T, Chen XY, et al. Selective estrogen receptor modulators (SERMs) for uterine leiomyomas. Cochrane Database System Rev. 2012;10: DOI: 10.1002/14651858.CD005287.pub4.
2. Geiser AG, Hummel CW, Draper MW, et al. A new selective estrogen receptor modulator with potent uterine antagonist activity, agonist activity in bone, and minimal ovarian stimulation. Endocrinology. 2005;146:4524-4535.