In some tissues, including normal endometrium, tamoxifen acts primarily as an ER agonist, accounting for its association with endometrial cancer.48-50 Given the differences in mechanisms of action, we speculate that when tamoxifen and goserelin are given in combination, the agonistic effects of tamoxifen may counteract the estrogen-depleting effects of goserelin. Here, ESR1 is linked to endometrial cancer.