Effect of adjuvant tamoxifen on the endometrium in women with breast cancer: a prospective study using office endometrial biopsy.

Purpose: To determine the frequency of developing abnormal pathologic changes in the endometria of tamoxifen-treated women. To characterize the type of pathologic changes involved.

Patients And Methods: Between October 1991 and September 1998, 159 patients initiating tamoxifen therapy for breast cancer confined to the breast and axillary lymph nodes were entered in a prospective study. In this study, office endometrial biopsies (EMBs) were obtained during the initiation of tamoxifen and at 6-month intervals for a 2-year period. Three subsequent annual EMBs were recorded for each patient, amounting to a 5-year surveillance.

Results: One hundred fifty-nine patients with a median age of 50 years were entered onto study. Patients were assessable if EMBs were performed at least 1 year after the initiation of tamoxifen treatment. Nine patients (5. 7%) were considered protocol violations. The remaining 111 assessable patients underwent a total of 635 EMBs (mean, 5.8 EMBs), with a median surveillance time of 36 months. Eighty-two (12.9%) of the 635 biopsies revealed tissue insufficient for diagnosis. Fourteen patients (12.6%) underwent dilation and curettage (D&C) for an abnormal EMB, persistent bleeding, or for evaluation of adnexal masses at the time of laparoscopy. Findings at D&C included complex hyperplasia (n = 1), abnormal histiocytes (n = 1), simple hyperplasia (n = 2), polyps (n = 4), endocervical polyp (n = 1), and decidualization (n = 2). Three D&Cs were negative. Three patients have undergone hysterectomy.

Conclusion: EMB was used to monitor the endometrium in the majority (95%) of breast cancer patients on tamoxifen in this trial, but the utility of routine EMB for screening in tamoxifen-treated women seems limited.