Dear spf: In general, antiestrogen therapy is recommended for 5 years following treatment for ER + breast cancer. Often postmenopausal women are offered aromatase inhibitors (such as arimidex) for which studies showed an advantage. Aromatase inhibitors cannot be used in premenopausal woman. Therefore, the options for a premenopausal woman could include tamoxifen, ovarian ablation (either by removal or chemically with lupron/zoladex), or even a combination of ovarian ablation and aromatase inhibitor. You should discuss with your oncologist the option(s) that would be best for your situation. If you are concerned, you could also get a second opinion.