A systematic review of randomised clinical trials - The safety of vaginal hormones and selective estrogen receptor modulators for the treatment of genitourinary menopausal symptoms in breast cancer survivors.

Therapies utilised in breast cancer management have been found to induce or worsen the genitourinary symptoms of menopause (GSM), a group of physical symptoms associated with the systemic loss of estrogen. These symptoms are often undertreated due to concerns surrounding cancer recurrence, especially when considering treatments with possible pro-estrogenic effects. As breast cancer prognosis continues to improve, clinicians are increasingly focussing on managing these symptoms amongst survivors. This systematic review primarily aimed to determine the risk of breast cancer recurrence amongst survivors using vaginal hormones and selective estrogen receptor modulator therapies recommended for use in GSM in the United Kingdom amongst currently published randomised clinical trials (RCTs). The secondary aim was to determine whether these RCTs demonstrated a significant rise in serum estrogen levels following the use of these therapies. A literature search revealed three RCTs suitable for assessment, two evaluating vaginal estrogen and one evaluating vaginal DHEA treatment. Our review determined that amongst published RCTs, no studies have aimed to assess for breast cancer recurrence; however among the studies observing for serious adverse effects of vaginal estrogen preparations, none have reported an increased incidence. Furthermore, these studies did not report a persistent or significant increase in serum estrogen levels following the use of vaginal estrogen products and low concentration (3.25 mg/day) DHEA gel. Larger RCTs studying commonly used vaginal preparations and selective estrogen receptor modulator treatments for GSM over longer follow-up periods will be vital to better assess the risk of breast cancer recurrence in survivors receiving these treatments.