ESR1 and breast carcinoma: In addition, although continuing tamoxifen therapy has been found to produce a reduction in recurrence and mortality for ER+ breast cancer [6], the patients treated with tamoxifen for a long time may suffer from side-effects, such as deep-vein thrombosis, endometrial cancer, pulmonary embolus, bone loss, stroke and genito-urinary system dysfunction [7–9].