The development of resistance to tamoxifen in patients with breast cancer: our experience

Background: The study used data from medical and counselling of patients who were diagnosed with hormone-dependent breast cancer. Aim: The objective of the paper is to identify within a group of patients diagnosed with hormone sensitive breast cancer and those who have received adjuvant tamoxifen, and then to isolate the patients with whom the therapeutic effect of tamoxifen stopped (resistance to tamoxifen). Methods: The study analyzed 153 patients in the period from 2005 to 2011, at the Public Health Institution Hospital, Sveti Vracevi" in Bijeljina. Resistance to tamoxifen was developed by 60 patients (39.2%) and 93 patients (60.8%) did not develop resistance to it. Results: More common emergence of resistance is in the premenopausal group of patients (p<0.001). Statistically significant difference in frequency of resistance to tamoxifen was observed in the group of patients with ER-/PrR+ status of steroid receptors (p<0.001). In relation to HER-2 status of diagnosed cancer, a statistically significant difference in frequency of resistance emergence during tamoxifen therapy in patients with HER2-positive status (p<0.001) was observed. We found that there is a statistically significant difference between patients with metastatic in lymph nodes compared to patients who had no metastases in lymph nodes (X 2 =39.494; p<0.001). Conclusions: The analysis of menopausal status of patients, status of ER/PgR receptors status, HER-2 status of diagnosed cancer and status of lymph nodes trying to sort out the parameters on the basis of which a group of patients who can be expected to develop resistance to tamoxifen could be differentiated.