Safety of using hormone replacement therapy in breast cancer survivors: A systematic review and metanalysis.

12067 Background: Improvements in breast cancer (BC) care have led to increased survival of patients; hence, more attention to long-term treatment-related adverse events and quality of life (QoL) is required. Symptoms of spontaneous and treatment-induced menopause significantly affect the QoL and adherence to endocrine therapy among BC survivors, with potential negative implications on outcome. Use of systemic hormone replacement therapy (HRT) to mitigate menopause-associated symptoms is not recommended to reduce the burden of these side effects being historically associated with an increased risk of disease recurrence. This systematic review and metanalysis aimed to estimate the effect of HRT on risk of disease recurrence in BC survivors. Methods: A systematic search of Pubmed and Embase libraries up to January 15, 2021, was conducted in order to identify randomized controlled trials (RCTs) investigating the risk of disease recurrence with the use of HRT in BC survivors. We used the random-effect model to calculate the overall risk of recurrence, reported as pooled hazard ratio (HR) with 95% confidence intervals (CI). Moreover, we performed a subgroup analysis to estimate the risk of recurrence according to hormone receptor status. The Higgins I 2 index was computed to assess the heterogeneity between studies. The likelihood of publication bias was assessed by Egger’s test. Results: Four RCTs were found and three were included in the metanalysis (n = 3.973 patients); one study (n = 100 patients) was excluded due to the impossibility to extract the HR for disease recurrence. Overall, 1.990 patients were randomized to receive HRT (estrogen-progesteron combination or tibolone), while 1.983 patients were included in control groups (placebo or no HRT). As compared to control group, HRT significantly increased the risk of BC recurrence (HR 1.49, 95% CI 1.15-1.93, p = 0.002). The heterogeneity between the studies was low (39%, p = 0.194), and no publication bias was found ( p = 0.537). Two studies reported the HR according to hormone receptor status. At the subgroups analysis, the risk of BC recurrence with the use of HRT was significantly increased in hormone receptor-positive patients (HR 1.8, 95% CI 1.15-2.82, p = 0.010) but not in those with hormone receptor-negative tumors (HR 1.25, 95% CI 0.83-1.88, p = 0.290). Conclusions: Use of HRT significantly increases the risk of recurrence in BC survivors, particularly in those with hormone receptor-positive disease. Therefore, this approach remains contraindicated in this setting. Alternative interventions to mitigate menopause-related symptoms should be proposed to these patients.