Long-term Tamoxifen Therapy for the Treatment of Breast Cancer.

Tamoxifen is a nonsteroidal antiestrogen that has become the frontline endocrine therapy for all stages of breast cancer. The drug is the only single-agent therapy that, when used in an adjuvant fashion, produces a survival advantage in postmenopausal women. Survival is longer when the estrogen receptor content of the primary tumor is higher, although receptor-poor patients still have a survival advantage from adjuvant tamoxifen equivalent to that noted with combination chemotherapy. The added advantages of tamoxifen are a maintenance of bone density and a decrease in fatal myocardial infarction. Although side effects from tamoxifen are few, patients must be examined for preexisting endometrial carcinoma before beginning drug use. Tamoxifen does not prevent the growth of endometrial tumors. Spotting and vaginal bleeding in postmenopausal patients taking tamoxifen should be followed up with a thorough gynecological examination. The incidence rate of endometrial cancer for tamoxifen-treated patients is 2 per 1000 patients per year. More than 80% of detected endometrial tumors are stage 1 disease and can be cured by hysterectomy.