Is screening for endometrial cancer necessary in asymptomatic women treated with tamoxifen for breast cancer?

Objective: This study aimed to investigate the endometrial pathology findings and to determine the appropriate diagnostic approach to assess for potential endometrial malignancy or premalignant pathology in women treated with tamoxifen for breast cancer. Methods: We retrospectively reviewed the medical records of 162 patients taking tamoxifen and who underwent endometrial biopsy. We compared the clinical features of the patients with endometrial intraepithelial neoplasia or cancer (EIN/EC group) and the patients with other pathologic results (others group). Results: ON or EC was found in ten patients (6.2%). While 70.0% of EIN/EC group received tamoxifen treatment for more than 3 years, 71.7% of the others group received less than 3 years (p < 0.001). Regardless of the presence of vaginal bleeding, EIN/EC was not found in patients with endometrial thickness (ET) <5 mm on transvaginal ultrasonography (TV-US). When ET was >= 5 mm, the incidence rates of EIN/EC were only 2.9% in asymptomatic patients and 11.6% in symptomatic patients, respectively (p = 0.002). When ET was >= 8 mm, the incidence rates of EIN/EC were 3.8% in asymptomatic patients and 12.0% in symptomatic patients, respectively (p = 0.002). When ET was <8 mm, EIN/EC was not found in patients without vaginal bleeding, while EIN/EC was found in 7.1% of patients with vaginal bleeding. Conclusions: Indiscriminate endometrial evaluation should be avoided in women treated with tamoxifen for breast cancer. Patients taking tamoxifen who experience vaginal bleeding and have a thick endometrium (>= 5 mm) on TV-US, they should undergo endometrial biopsy.