Despite the benefits of tamoxifen in preventing breast cancers from returning, it does have side effects. Women taking tamoxifen can experience side effects similar to menopausal symptoms, such as night sweats and hot flushes.Rare but serious side effects of tamoxifen include increased risk of endometrial cancer (cancer of the lining of the uterus), blood clots, and stroke.In this study no increase in the incidence of stroke was observed with 10 years of tamoxifen therapy, though endometrial cancer risk was higher in this arm.ews_treatment-4.jpg. Women with oestrogen receptor positive breast cancer who take tamoxifen for 10 years halve their subsequent risk of dying, according to new research being presented at this year’s ASCO conference.