The effect of tamoxifen on estradiol, SHBG, IGF-1, and CRP in women with breast cancer or at risk of developing breast cancer: a meta-analysis of randomized controlled trials

Background and aim: The effects of tamoxifen on the serum levels of hormones and acute phase reactants have been studied previously, but study results have been inconsistent, especially in women with breast cancer. Hence, we conducted this meta -analysis of randomized controlled trials (RCTs) to try to clarify the effects of tamoxifen on estradiol, insulin -like growth factor 1 (IGF-1), sex hormone binding globulin (SHBG), and C -reactive protein (CRP) serum levels in women with breast cancer or at risk of developing breast cancer. Methods: Databases were systematically searched up to December 2023. The meta -analysis was generated through a random -effects model and is presented as the weighted mean difference (WMD) and 95 % confidence intervals (CI). Results: Nine publications were included in the present meta -analysis. The comprehensive findings from the random -effects model revealed an elevation in estradiol (WMD: 13.04 pg/mL, 95 % CI: 0.79, 25.30, p = 0.037) and SHBG levels (WMD: 21.26 nmol/l, 95 % CI: 14.85, 27.68, p = 0.000), as well as a reduction in IGF-1 (WMD: - 14.41 mu g/L, 95 % CI: -24.23, -4.60, p = 0.004) and CRP concentrations (WMD: -1.17 mg/dL, 95 % CI: -2.29, - 0.05, p = 0.039) following treatment with tamoxifen in women with breast cancer or at risk of developing breast cancer, with no impact on IGFBP-3 levels (WMD: 0.11 mu g/mL, 95 % CI: -0.07, 0.30, p = 0.240). Conclusion: Tamoxifen administration seems to increase estradiol and SHBG levels and reduce CRP and IGF-1 levels in women with breast cancer or at risk of developing breast cancer. Further studies are needed to determine whether these changes have any clinical relevance.