Effects of adjuvant tamoxifen on the endometrium in postmenopausal women with breast cancer: a prospective long-term study using transvaginal ultrasound.

To study the value of transvaginal ultrasound (TVS) in endometrial screening of postmenopausal breast cancer patients treated with tamoxifen. In 247 tamoxifen-treated (20 to 30 mg/d for >/= 2 years) women and 98 controls, the endometrium was prospectively followed-up by means of TVS every 6 months for up to 5 years. Patients with homogeneous endometrium of more than 10-mm thickness were then scanned repeatedly every 3 months. The mean endometrial thickness was 3.5 +/- 1.1 mm before treatment and increased to a maximum of 9. 2 +/- 5.1 mm after 3 years of tamoxifen application (P: <.0001), which was significantly (P: <.0001) thicker compared with controls. Fifty-two asymptomatic patients with thickened or morphologically suspect endometrium underwent hysteroscopy and dilatation and curettage (D&C), resulting in four uterine perforations. Histopathologically, atrophy was found in 38 patients (73.1%), polyps in nine, hyperplasia in four, and endometrial cancer in one case. In 20 screened patients who reported vaginal bleeding, five atrophies (25%), five polyps, four hyperplasias, and two endometrial cancers were found. Before hysteroscopy and D&C were performed, 36 (69.2%) of 52 asymptomatic and four (20%) of 20 symptomatic patients were scanned by repeated TVS over 2 to 30 months. Invasive diagnostic procedures were significantly (P: <.05) more frequent in younger and obese patients. In the controls, one asymptomatic polyp and one symptomatic hyperplasia were found. In tamoxifen-treated patients, TVS offered a high false-positive rate, even with a cutoff value of 10 mm for endometrial thickness and repeated TVS scans. Increased iatrogenic morbidity and only one asymptomatic endometrial carcinoma do not warrant endometrial screening by TVS in tamoxifen-treated patients.