THE INCIDENCE OF SUBSEQUENT ENDOMETRIAL CARCINOMA WITH TAMOXIFEN USE IN PATIENTS WITH PRIMARY BREAST-CARCINOMA

BACKGROUND. Tamoxifen commonly is used as adjuvant therapy for all sta ges of breast carcinoma. However, several studies have suggested an as sociation between the use of tamoxifen in breast carcinoma patients an d the subsequent development of endometrial carcinoma. The objective o f this study was to determine the relation between long term tamoxifen usage and the risk of endometrial carcinoma in patients with breast c arcinoma and to determine whether the increase in the cumulative incid ence of endometrial carcinoma observed in previous studies is a true i ncrease. METHODS. Eight hundred and twenty-five patients with primary breast carcinoma who underwent annual gynecologic examination and canc er screening were reviewed. None of the patients had undergone hystere ctomy or received any prior estrogen replacement therapy. These patien ts underwent a pelvic examination and cytologic and/or histologic scre ening of the cervix and endometrium every year wen if they had no gyne cologic symptoms. The dose of tamoxifen, length of tamoxifen treatment , and potential confounding variables were recorded. The relative risk of subsequent endometrial carcinoma in patients with primary breast c arcinoma was analyzed by the Cox proportional hazards model. RESULTS. Thirteen of the 825 patients developed a subsequent endometrial carci noma. The cumulative incidence of endometrial carcinoma was 1.58%. Fou r of 13 patients who subsequently developed endometrial carcinoma rece ived tamoxifen and 9 had not received tamoxifen. The relative risk of endometrial carcinoma by total dose of tamoxifen exposure was 1.0001 ( P = 0.0145). There was no statistically significant correlation betwee n the cumulative dose of tamoxifen or the length of tamoxifen treatmen t and the histologic type and grade of endometrial carcinoma. In addit ion, there was no statistical difference in the prognosis of endometri al carcinoma between the patients who received tamoxifen and patients who did not. CONCLUSIONS. The results of this study show that tamoxife n use does not appear to increase the incidence of subsequent endometr ial carcinoma in patients with primary breast carcinoma who underwent annual screening for gynecologic carcinoma. (C) 1998 American Cancer S ociety.