Endometrial cancer after Tamoxifen treatment of breast cancer. Results of a retrospective cohort study

Purpose. The aim of the present retrospective study was to evaluate the relationship between the use of Tamoxifen (TAM) and development of endometrial carcinoma (EC) in Slovenia women patients (pts). Methods: This retrospective study included 408 pts, aged 55 years or more, treated for invasive breast cancer (285 pts were treated with TAMI 123 pts without it) at our Institute from 1988 to 1992. The pts who had had hysterectomy were not included. The observation period was 5 to 9 years. The Mantel-Haenszel chi(2) test and Fisher p test were used. Survival was computed by Kaplan-Meier estimates. Results: As to the most common risk factors of EC no statistically significant difference was observed. The daily dose of TAM was 20 mg, median treatment period was 38 months (1-97). In 15% of pts, TAM-related side-effects were noted 30 months later; the most common was uterine bleeding. EC was detected in 10/30 pts with curettage, while others had polypous changes and cystic hyperplasia. In the group of pts without TAM, curettage was performed in 4 pts. In view of curettage, the difference between the two groups was statistically significant (p=0.014). In the group of pts without TAM, EC was detected in 2 pts. Evaluated relative risk (RR) was 2.16 (0.48-9.70). Between the TAM groups of pts with and without EC, the difference in survival was minimal, statistically nonsignificant (p=0.41). Conclusion: Treatment with TAM increases the risk of benign endometrial changes and EC. In EC cases treatment with TAM does not influence the pts survival. Pts using TAM need to know what symptoms and signs should be reported.