Early and late tamoxifen resistance in breast cancer

Abstract

In our study we investigated the role of the estrogen receptor (ER), progesterone receptor (PR) and clinicohistological parameters in breast cancer patients treated with tamoxifen during the early (2.5 years) vs. late (2.5-5 years) follow-up. The negative status of both ER and PR and tumors equal to or bigger than 2 cm defined the phenotypes and consequently the groups of patients with the worst clinical course of the disease: ER-negative PR-negative, ER-negative pT2 and PR-negative pT2. These high-risk subgroups were related to early follow-up indicating de novo resistance. It is relevant to point out that examined predictive indicators did not show significant importance in the late follow-up study.