Postmarketing adverse events of tamoxifen in male and female patients with breast cancer

Abstract Tamoxifen (TAM), a selective estrogen receptor (ER) modulator, has received approval for use in patients with breast cancer (BC) exhibiting positive ER expression. Given the widespread clinical use of TAM, a comprehensive real‐world study of its adverse events (AEs) is warranted. The database for analysis, sourced from the Food and Drug Administration Adverse Event Reporting System (FAERS), covers the period from the first quarter of 2014 to the third quarter of 2023. A disproportionality analysis was conducted to quantify the correlation between TAM and AEs. Subgroup analyses were performed to identify differences between BC AEs in males and females receiving TAM, aiming to assess the risk factors of male BC AEs. Total 4890 reports indicated BC, with 91 and 4190 specifically linked to AEs in male and female patients with BC, respectively. Male‐specific AE was libido decreased (reporting odds ratio [ROR]: 43.33), and female‐specific AE was uterine disease, including sarcoma uterus (ROR: 519.51), endometrial cancer (ROR: 131.26), uterine polyp (ROR: 40.83), endometriosis (ROR: 11.39), among others. A notably higher risk of AEs in male patients with BC was observed in individuals aged >65 years ( χ 2 = 20.83, p < .001). Male patients with BC had a relatively higher risk of hospitalization ( χ 2 = 4.83, p = .03) and a lower risk of deaths ( χ 2 = 5.32, p = .02). Theses finding may assist healthcare professionals in recognizing the TAM‐associated AEs and understanding gender differences, potentially improving safety in clinical applications.