Endometrial Evaluation in Patients With a History of Tamoxifen Use: Is an Evidence-Based Approach Utilized? [ID 867]

INTRODUCTION: Tamoxifen is a common adjuvant therapy utilized in patients with breast cancer. Despite antagonistic effects in breast tissue, tamoxifen has agonistic properties in the endometrium that may increase risk of endometrial hyperplasia and carcinoma. Asymptomatic endometrial evaluation is not an effective screening tool; however, it is still utilized in this patient population. We aim to identify patient and provider associations with asymptomatic evaluations of the endometrium. METHODS: We performed a retrospective cohort analysis of patients with breast cancer who received tamoxifen between 2012 and 2022 at a single institution. Variables of interest included demographic and clinical characteristics as well as endometrial evaluation (pelvic ultrasound or endometrial sampling [EMB]). Descriptive statistics, Fisher’s exact tests, and logistic regressions were calculated. RESULTS: A total of 117 patients were included. Of these, 54 (46.1%) patients had endometrial evaluation at or after the time of tamoxifen initiation. Of these 54 patients, 15 (27.8%) did not have abnormal uterine bleeding (AUB). Ten patients underwent EMBs without AUB; all were benign without hyperplasia. Patients without AUB were 72% less likely to be referred for endometrial evaluation by obstetrician–gynecologists compared to other providers (odds ratio 0.28; 95% CI [0.08, 0.98]). No differences in age, body mass index, menopausal status, smoking status, or duration of tamoxifen use were seen between evaluated patients with and without AUB. CONCLUSIONS/IMPLICATIONS: A quarter of breast cancer patients using tamoxifen in our cohort underwent unnecessary endometrial evaluation. The difference in provider referral patterns may indicate a need for distribution of evidence-based guidelines for endometrial evaluation on tamoxifen.