Prevention of repeated benign endometrial pathology in postmenopausal women with breast cancer and tamoxifen-induced endometrial pathology: A randomized trial comparing anastrozole and tamoxifen

Abstract

584 Background: To study the effects of anastrozole versus tamoxifen in postmenopausal breast cancer patients with hormone-sensitive breast cancer and histologically proven, tamoxifen-induced benign endometrial pathology. Methods: A total of 171 tamoxifen-treated (20 mg/day >12 months) patients with abnormal vaginal bleeding (n=83) or thickened endometrium (demonstrated by transvaginal sonography, TVS), and subsequent histological clarification by hysteroscopy and dilatation and curettage (D&C;), were randomized to tamoxifen or anastrozole. Patients were monitored using TVS at 6-month intervals for up to 42 months. Results: There were no differences with respect to numbers of patients, tumor characteristics, endometrial thickness (tamoxifen: 12.9 ± 5.6 mm; anastrozole: 12.3 ± 5.8 mm) and histological findings before randomization. However, only 6 months after randomization, endometrial thickness in patients randomized to the tamoxifen arm differed significantly (6.7 ± 2.4 mm) from that of the anastrozole arm (3.3 ± 1.2 mm, p<0.0001). In 29 (33%) of the patients randomized to tamoxifen, a repeated hysteroscopy and D&C; was necessary, revealing 14 polyps, eight hyperplasias and seven atrophies. In the anastrozole arm there were four patients with vaginal bleeding, leading to repeated hysteroscopy and D&C; (p<0.0001). The results of the first and second histological assessments were consistent in 21 of 33 patients (63.6%; p=0.003). Although there were significantly lower numbers of endometrial changes and life-threatening side effects in anastrozole-treated patients, the cost–benefit analysis for endometrial changes was unfavourable for anastrozole-randomized patients (cost ratio = tamoxifen:anastrozole = 1:5). Conclusions: In breast cancer patients with tamoxifen-induced endometrial abnormalities, anastrozole represents an effective treatment for the prevention of repeated endometrial pathology. No significant financial relationships to disclose.